I for many years have been wanting to grow american persimmon or pawpaw and i have purchased seed from different sources and cold stratified it but had no germination. my guess is much like pawpaw the seeds should not be aloud to dry soo if anyone out there is willing to sell me some spoiled fruit from either american persimmon or pawpaw so i can extract seed i would purchase it from you. 😆

Pawpaw is only hardy to zone 5. So your zone 4b will most likely not work.
Pawpaw are not self-fertile so you will need different cultivars for fruit.
https://www.greenbarnnursery.ca/products/paw-paw-taylor

Here is a persimmon plant that you might like hardy to -40C
https://www.greenbarnnursery.ca/collections/cold-hardy-exotics/products/campbell-grafted-persimmon

With these expensive plants as starters you can then save seeds and then grow your own.

I can't say as I'll ever get fruit but I have a couple small pawpaws growing unprotected in Canadian climate zone 4B for about four years now.