Found Creatures

While the spirit you summon with find steed or find familiar may not be a creature, they "take the form of an animal" that is a creature.

This is confirmed by Sage Advice (v. 1.14 p. 14 - emphasis mine):

Does the familiar of find familiar count as an ally for the purposes of Sneak Attack? A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.

These creatures can be polymorphed.

If you are using these creatures as sources for objects to become spell components, it seems on the face of it that you would be limited to one use only, because:

You can't have more than one familiar at a time. If you cast this spell while you already have a familiar, you instead cause it to adopt a new form.

and

You can't have more than one steed bonded by this spell at a time.

However, this depends on your DM's ruling about whether modifying the object counts as damage, and how damage to objects interacts with the true polymorph. This question asks whether polymorphing a creature into a twig and then breaking the twig in half would end the spell. This question assumes that if you polymorphed a creature into metal, you could melt the metal and reform it into numerous separate items without ending the spell.

Thus, depending on your DM's rulings, it might be possible to polymorph your familiar or steed into as large a single object of component as possible, and then divide the object, harvesting the pieces for use as multiple sets of components. The DM would then limit the number of times you could divide it before the object's hp reached zero and the spell was ended.

The object's size is limited by the size of the form of the creature:

Creature into Object. If you turn a creature into an object, it transforms along with whatever it is wearing and carrying into that form, as long as the object’s size is no larger than the creature’s size.

Since the limit is the original size, you will clearly get more from find steed here than you would from find familiar (and even more if you can cast find greater steed). However, note that the limit is size, not value. Even a size small familiar, polymorphed into a solid block of diamond, might be mined for numerous component gemstones with gem-cutter's tools or the fabricate spell.

Found Creatures

While the spirit you summon with find steed or find familiar may not be a creature, they "take the form of an animal" that is a creature.

This is confirmed by Sage Advice (v. 1.14 p. 14 - emphasis mine):

Does the familiar of find familiar count as an ally for the purposes of Sneak Attack? A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.

These creatures can be polymorphed.

If you are using these creatures as sources for objects to become spell components, it seems on the face of it that you would be limited to one use only, because:

You can't have more than one familiar at a time. If you cast this spell while you already have a familiar, you instead cause it to adopt a new form.

and

You can't have more than one steed bonded by this spell at a time.

However, this depends on your DM's ruling about whether modifying the object counts as damage, and how damage to objects interacts with the true polymorph. This question asks whether polymorphing a creature into a twig and then breaking the twig in half would end the spell. This question assumes that if you polymorphed a creature into metal, you could melt the metal and reform it into numerous separate items without ending the spell.

Thus, depending on your DM's rulings, it might be possible to polymorph your familiar or steed into as large a single object of component as possible, and then divide the object, harvesting the pieces for use as multiple sets of components. The DM would then limit the number of times you could divide it before the object's hp reached zero and the spell was ended.

The object's size is limited by the size of the form of the creature:

Creature into Object. If you turn a creature into an object, it transforms along with whatever it is wearing and carrying into that form, as long as the object’s size is no larger than the creature’s size.

Since the limit is the original size, you will clearly get more from find steed here than you would from find familiar (and even more if you can cast find greater steed). However, note that the limit is size, not value. Even a size small familiar, polymorphed into a solid block of diamond, might be mined for numerous component gemstones with gem-cutter's tools or the fabricate spell.

Found Creatures

While the spirit you summon with find steed or find familiar may not be a creature, they "take the form of an animal" that is a creature.

This is confirmed by Sage Advice (v. 1.14 p. 14 - emphasis mine):

Does the familiar of find familiar count as an ally for the purposes of Sneak Attack? A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.

These creatures can be polymorphed.

Found Creatures

While the spirit you summon with find steed or find familiar may not be a creature, they "take the form of an animal" that is a creature.

This is confirmed by Sage Advice (v. 1.14 p. 14 - emphasis mine):

Does the familiar of find familiar count as an ally for the purposes of Sneak Attack? A familiar is an allied creature. Its proximity to a target can allow you to use the Sneak Attack feature or any other feature that requires the presence of an ally.

These creatures can be polymorphed.

If you are using these creatures as sources for objects to become spell components, it seems on the face of it that you would be limited to one use only, because:

You can't have more than one familiar at a time. If you cast this spell while you already have a familiar, you instead cause it to adopt a new form.

and

You can't have more than one steed bonded by this spell at a time.

However, this depends on your DM's ruling about whether modifying the object counts as damage, and how damage to objects interacts with the true polymorph. This question asks whether polymorphing a creature into a twig and then breaking the twig in half would end the spell. This question assumes that if you polymorphed a creature into metal, you could melt the metal and reform it into numerous separate items without ending the spell.

Thus, depending on your DM's rulings, it might be possible to polymorph your familiar or steed into as large a single object of component as possible, and then divide the object, harvesting the pieces for use as multiple sets of components. The DM would then limit the number of times you could divide it before the object's hp reached zero and the spell was ended.

The object's size is limited by the size of the form of the creature:

Creature into Object. If you turn a creature into an object, it transforms along with whatever it is wearing and carrying into that form, as long as the object’s size is no larger than the creature’s size.

Since the limit is the original size, you will clearly get more from find steed here than you would from find familiar (and even more if you can cast find greater steed). However, note that the limit is size, not value. Even a size small familiar, polymorphed into a solid block of diamond, might be mined for numerous component gemstones with gem-cutter's tools or the fabricate spell.