It costs ~2gp (depending on the mood of the shopkeeper) from any goods store and:
A backpack can hold one cubic foot or 30 pounds of gear. You can also strap items, such as a Bedroll or a coil of rope, to the outside of a backpack.
This should be enough to carry most things, and you arent limited to carrying one. But if you dont want to be encumbered all the time, magic items are the way to go.
If you are lucky enough, you might be able to loot a Bag of Holding, or a Portable Hole or a Handy Haversack.
The Handy Haversack will hold 120lbs or 12 cubic feet will be much more than you need for all the stuff you listed there. DMG page 152.
This Backpack has a central pouch and two side pouches, each of which is an extradimensional space. Each side pouch can hold up to 20 pounds of material, not exceeding a volume of 2 cubic feet. The large central pouch can hold up to 8 cubic feet or 80 pounds of material. The Backpack always weighs 5 pounds regardless of its contents.
The Portable Hole creates a hole 10 foot deep with a diameter of 6 feet. This makes it your best option as it can hold the most and has no weight limit. DMG page 184.
... It unfolds into a circular sheet 6 feet in diameter.
You can use an action to unfold a portable hole and place it on or against a solid surface, whereupon the portable hole creates an extradimensional hole 10 feet deep. The cylindrical space...
The bag of holding is also very good. DMG page 173.
This bag has an interior space considerably larger than its outside dimensions, roughly 2 feet in diameter at the mouth and 4 feet deep. The bag can hold up to 500 pounds, not exceeding a volume of 64 cubic feet. The bag weighs 15 pounds, regardless of its contents. Retrieving an item from the bag requires an action.
All of these items are magic items, except the backpack, and cannot be bought and are quite rare (usually), so its unlikely that you will come across them anytime soon, unless your DM is really nice. Best bet is to buy 2 backpacks and carry them with you instead of searching for magic items. You can always drop them before you run into a battle so you aren't encumbered.