Ive beaten the game 3 times searching the animal that druid dude wants in the Shattered Hand. Ive tried the squirrel in Easthaven, the cows the alchemist has in Kuldahar, the squirrel in Easthaven after Poquelin destroys it, the animals that are next to Poquelin in Lower Dorn's, Ive even tried resurrecting the dead cat your sometimes get from Jester's Endless Bag. Whoever reads this and knows where this lost animal that needs a home let me know PLEASE!

There's a drow merchant living among the dark dwarves in the forge area of Dorn's Deep. If you go up the lift and talk to the leader of the dwarves up there and get him some food, he'll ask you to rescue his people that are trapped by umber hulks to the northeast. Once you beat the hulks, there's a door in the rock that leads to a small village. The drow should be the first person you come across. He has a cage of birds and a cage of small animals you can purchase, and these can be taken back to the Hand to help the aboretum.

Dammit, I killed the drow after glancing at his inventory. I should be more careful! :(

Um yeah, especially with the way the final part of the game plays out -- that drow is your last chance to stock up before the final few battles (unless you feel like taking the time to truck back to the Hand or Kuldahar).