Shoe, I would just go ahead and buy the vintage. Wait for a clean one in your size and bid on it.
Signs I look for are minimal scraping on the outsole (dead stock is of course better but they usually go over $200), no signs of walking through a puddle, and a clean insole. Something like this is usually $100-$150.
Yep on ebay.
the great thing about florsheim imperials is that there were so many of them back in the day, but can you imagine anyone actually throwing any away? They are indestructible, I'm sure 90% went to thrift stores. They all come up eventually.