They are all farmed...Only rarely is a Gold or white fish found in the wild.
All of these ones in the hobby are being produced in aquaculture facilities. If I remember the odds correctly it is one in five thousand Tropicus that turn out white or Piebald in a given spawn. Given the fact a big mature female can lay 6,000+ eggs with 80% survival those are pretty good odds. I would not think the odds are any different for Alligator or Florida gars, naturally the amount of fry produced for a Gator or a Florida are slightly different.