Most Rainbow breeders sell through aquabid. But it's hit and miss, it's not like they always have something available.
Here are a few I would recommend-----
Johnnyb, Rfman, alloddballaquatics, Roseline
There can be big difference in the adult color of poor quality to higher quality fish. Starting with good stock is recommended. Boesemani are a prime example. I've seen them anywhere from a yellow/grey combo to orange/blue. Some lines have almost an orange reddish color, really beautiful. A yellow/grey young Boese does not mature into a orange/blue.