Clean the motor and see if you are lucky enough to find a sticker with the speed, amps, and other information on it. The motor MIGHT be more or less standard. It's possible that the exact motor is still in use in something else. Others here are good at tracking down older parts and they might have more sources to offer you.
If that doesn't work then check in the phone book and see if someone in your area rebuilds AC motors. A good grinding, brushes, and a set of bearings and maybe some other minor repairs could get the original motor working like new.