I believe that the most common practice on C22s is to upgrade the diameter and material of the shrouds. Most of them would have come with 1/8" 304 from the factory, and most replacements today are 5/32" 316. I'm no metallurgist, but I was told that 316 is more resistant to corrosion but not quite as strong as 304, which is why they upsize it by a 32nd.
You probably could get replacement wire from a place other Catalina Direct, but you'd have to make very certain that it was actually the same thing, with the right type of stainless and the right strand count, and then you'd also need to have a way to swage on all of the fittings--and do a really good job of it. It's likely easier and more likely to succeed if you let Catalina Direct (or a local professional rigger) do it.
Letting the rig get and stay very loose is bad because it allows the wire to bend back and forth through a large swath, and like bending a paperclip over and over, it can get weak and break prematurely. If that's what happened in your case, I wouldn't trust any of the shrouds or stays.