Ah, that's the real question! I compiled the list from a booklet that lists all livebearers and whether they are kept by some people. Those mentioned are kept, mostly by active livebearer hobbyists. I think most of them might be available only through the respective livebearer associations.
Yes, I might have just gone a bit overboard there,

I agree. Got a bit carried away while planning my pico and looking for suitable fish for it!
I think I'll put a * before those that are most likely most easily available. That ok idea?
EDIT: Just did that..