Are there any items that allow the wielder to possess another as if casting the spell Possession?
Pathfinder or D&D 3.5 items are accepted.
The most common magic item (and only item that a casual perusal of the DMG, Magic Item Compendium, Complete Mage, Complete Arcane, and a few other books I checked can find) is the Scroll of Magic Jar; DMG p.240. The spell is in the PHB, p.250.
It has the advantage of being a published magic item. It has the disadvantage of being usable by wizards and sorcerers and the UMD skill only.
However, if that is not to your taste, it is trivially simple to create your own item using the official rules for magic item creation in the DMG. Items created using these rules are technically official, if custom. (DM approval still required.)
A command word item with a customary item body slot (probably head, maybe neck) and once per day usage costs:
= 16,200 gp.
Double the cost if it doesn't require a body slot (like many wondrous items).
Keep in mind that the magic jar spell requires a gem, so your item should either be a gem, or include one.
For flavor, I suggest the Crystal Skull of Doom.
The Diadem of Control allows you to take possession of constructs.
The wearer of the headband can assume direct control of the construct as a full-round action, controlling all of the construct’s actions as possession. The wearer can end this control at any time as a free action. The wearer can remove the crystal from a construct as a standard action, allowing the wearer to use the crystal on a different construct and returning control of the construct to its original master.
Also, magic staves with the Possession spell should also allow that, as long as the spell is also on the character's spell list. However, none of the officially published staves come with the spell. Unlike wands, spells cast from staves uses the owner's ability scores to set the spell's DC, which work much better for offensive spells like this.
Other than that, there are no published items that allow you to affect a creature with Possession, not even among artifacts. Your best bet would be to summon a creature that has that ability using a magic item, like an Ataxian, Avatarana, or Psychemental.
Being published in the Occult Adventures, Possession does not exist in D&D 3.5. Your closest bet being the Magic Jar spell (also 5th level), which is also a relatively stronger effect and different mechanics.
Possession was created to allow an earlier effect at "possessing" a creature, which you had to rely on specific monster abilities (such as a Ghost's) or mimic Magic Jar and add restrictions and exceptions at how it works.
For instance, there is no "gem" (receptacle), you can't "hop" between bodies, the target's soul isn't ejected from the body, you are not ejected to a gem if the creature dies, and there is no risk of getting killed by being too far from your body. But other than that, those two spells are very similar.
Considering this, you could look up at any published magic items that use Magic Jar and replace it by Possession and the item would still behave very similar to how you want. For instance, the Summon-slave Crystal allows you to use magic jar on your summoned creatures once per day, and the Orisian Spirit Jars will allow you to swap your soul between three jars and whoever you targeted with your Magic Jar spell.
How, again, none of the published magic items allow you to cast Magic Jar either.