Have you tried England's?

Here is a link that might be useful: England's Orchard link

Looks like EL has them in stock.

Here is a link that might be useful: http://ediblelandscaping.com/products/trees/Pawpaws/

Have you tried Nolin River, Burnt Ridge, One Green World, Raintree? Probably a few others that I can't think of right now.

Jim Gilbert of One Green World said last weekend that they have them, potted, in stock when I asked if they had brought some trees to the All About Fruit Show (where they were giving samples of the pulp and of professionally made pawpaw gelato).