What types of ferrets are there besides Marshall's?

I'm possibly looking into purchasing a ferret, but a long lifespan is absolutely crucial to me. I've heard that the most common ferrets, Marshall's ferrets, are easiest to come by, but can live half the time as the other ferrets, and are usually inbred and easily develop things like cysts, or other medical problems. I live in Scottsdale Arizona. Where can I look for ferrets that I can trust should have long, healthy lives? I know some ferrets can even live to be 20, and even a lifespan to 15 would be great for me. If Marshall's ferrets are the inbred, lower-quality ones, what other "breeds" should I look for that will result in the kind of quality pets I'm after? Any links to or names of breeders or other sources for ferrets would be great. Thank you very much!