Interesting old guns, fairly rare. I've got one, been in the family longer than anyone remembers. They say you must only use black-powder shells, but I didn't know until recently, so I've put everything (except b-p) through it over the past 40 years ! However, it's best to play safe nowdays. In my humble opinion, I think the real reason why Winchester re-called them is because the hammer can still drop when the breech block is not quite locked. Happened to my Pop, no harm done, but he didn't touch it for ten years after that little surprise.

Have you tried Bob's Gun Shop http://www.gun-parts.com/cowboyguns