Diccuric/The merchants

When you meet Homer he'll tell you about his new trade as a merchant. He'll tell you that there are others in the camp that will trade with you, but only if you're carrying an item they desire.

Fisk
Fisk wants wolf pelts, and Homer happens to sell them. Once you have the wolf pelts simply go up to Fisk and he'll offer to trade with you; from this point onwards you can trade with him whenever you like, even if you don't actually sell him the pelts.