Well new guy, I know I'm answering this a little late, but I've always said anything that is hard to impossible to make, or at least make well:

Small metal items- needles, pins, fishhooks, paperclips, nails, wire.

Cordage- everything from sewing thread to fishline to paracord to clothesline to hawser.

Salt.

Hand tools.

Basically, if you are the Americas, look to see which trade goods other than booze and firearms were the most in demand by the indigenous tribes in your area.