Cold stream farms has a bunch of stuff, I believe they are in Michigan as well. https://www.coldstreamfarm.net/ 

 I was going to suggest these guys. They are north of Ludington, so this wouldn't be too far away. 

I have not purchased trees from here yet, but have heard good things. I'll probably put in a fall order soon.  

 I’ve been in search for the trees too, Nick Ferguson sold them a couple years ago at rare plant store, but I had just missed buying them and I haven’t seen him sell them since 

 I wonder if @rev.hodl has any? 

 @reltbracco 🫂💜 

 Sorry, I only know about a source in Virginia. Good luck 💚 

 https://sawyergardencenter.com/catalog/222401/produce

Not sure about pawpaws but this place has a massive selection of local produce.  If they don't have it could probably point you in the right direction.  If you gave them a call they could probably help. 

 I've got two trees I can sell right now. I'll bring them to the next swmi meetup if you want them.  

 I will be harvesting pawpaw soon and can have seeds available too. I've had good success growing them from seed.