I have played through IWD twice, and i havent yet come across any...are there a merchant i have missed?

Yes, you missed a merchant. He's in the entrance to Dorn's Deep, the map with the Ettins and the Blue Myconids. In a tower in the northeast. After you find the razorvine extract for him, you can get a dialog option to trade. You might have done the razorvine quest, but I think you have to initiate a new conversation with him after that to get the trading option. I would have missed it but for the hint book.

IIRC, he sells Feeblemind, all the Conjure Elemental spells, and Summon Shadow. Also a few potions.