The .22 rf isn't really taken seriously in this country. I doubt you'll be able to find anything, but you might do a search for aftermarket triggers and check their websites. You could get a leg up by using Brownells to find firms who make replacment triggers/parts (Timmny, Power Custom, Rifle Basix etc.) and hitting their own websites.
There are aftermarket pieces available for the Ruger 10-22 and Remington 597, but not much else.
