I find them very occasionally at our farmers market here in Southern Germany.
It's strange there's three different fruits called a pawpaw. The Pawpaw/Carica papaya (called Papaya in North America), the Mountain Pawpaw/Vasconcellea pubescens, and the American Pawpaw/Asimina triloba (which this article is about).
It would seem you probably don't see these in Germany.
Except that we also see the occasional NFL season game in the stadium, why not an Indiana banana too? In these days of international logistics, it seems anything is possible. :-)