I have some seeds I would be willing to trade for other seeds harvested in zone 3 or colder, mine are from 2b.
I have beaked hazelnut, a small green
apple that stores well, buffalo berry, caravans,
should be able to get sea buckthorn, Manitoba maple, green
ash, Siberian elm. I'm sure there are others that I could get/find.
I'm looking for in particular a larger kind of hazelnut, a cold hardy black walnut, apricot. If your not sure you have something just speak up don't be afraid to ask.