I see carbines at every gun show, and I know one gun shop that usually has four or five. Some are over priced, but there are some reasonable ones out there if you just want a shooter. I would stay away from commercial carbines, though; there is about zero collector value, and they are not always well made or reliable.
Problem is that carbines have caught fire as collector items, and prices have gone up, even on "mixmaster" guns as people want to "restore" them.
Jim