I looked at the Goodwill Outlet near my home yesterday and found exactly one instrument that had cassette players included. I plugged it in and found a tape to put in it to test it and no sound came out. Can't quite trust that. I will check other thrift stores, though. I think that's the most likely source right now. Even ebay had almost nothing.
Oh, and speaking of chorale performances, this is what we are doing this Saturday: