physically unremovable items

[sreservoir]

For item familiar protection. How does using a psychoactive skin of proteus as the item sound? What other, cheaper unremovable items exist?

[Coidzor]

For item familiar protection. How does using a psychoactive skin of proteus as the item sound? What other, cheaper unremovable items exist?

Well, I wouldn't call several levels of bone knight cheaper, but losing the armor from that class requires killing you, so the bone armor from that class might fit your criteria.

[The Glyphstone]

There are a number of very cheap grafts, though I believe they count as nonmagical after attachment and so can't be Item Familiar-ed.

[Cog]

Warforged Embedded components can be pretty cheap. I have a vague memory of crystals that Kalashtar could shove into their heads, too.

[Claudius Maximus]

Yeah the embedded shards are quite difficult to remove.

You could always make it a powerfully cursed item. Quite hard to get rid of those sometimes. Also I'm sure there could be some cool stories behind it.