I'm hoping to be able to trade a battle-stone with someone. I know that this will only work for non pet-battle pets, but hopefully we'll be able to work out a trade. I have elemental and beast stones, and am looking for humanoid.
How I've done this previously is you can crate your pet (hence not being able to use trapped pets), trade it to me, I add it to my collection, then use the stone on it. I then recrate it and trade it back, then you do the same for me. A bit of trust is required, but I figured anyone using these forums can be trusted regarding their pets!
Feel free to ingame mail me, the character with the stones (hah!) is Principa, Alliance on Bleeding Hollow.