Look around a bit and you should find one without too much difficulty. They're not all that rare, and they do change hands reasonably frequently because many people who buy them shoot a few cylinder-fulls then sell them. At a recent gun show I found two, both like new. There was a big difference in price, though. One was $425 (way too much, IMO) and the other was under $300. I notice the one above has one bid at $300 and that's below the reserve. Shop around some.
You should make sure you ID a source for the moon clips. They don't last forever (they eventually bend or cup), and they're easy to lose.