google is your friend http://hubcapmike.com/1957-cadillac-wheel-covers-hubcap.html oops. I just read that you're looking for an alliance vendor who sells 'em. My bad.
If you have alot of money .I know a guy that has n.o .s.Caddillac hubcaps ,They are mint He wants between 800 -900 for them .If interested pm me...chrome perfect ,straight Concours quality