I know that Don Soderberg at SMR offers some Leucistic Black Rats and Leucistic Texas Rats (located here). I think he says the only difference is the size and the disposition. Other than him, I don't really know of anyone who sells them, although there are definitely breeders out there. Check around at the next expo you go to. As for if they can breed with corns... probably? but don't take my word on that. Ask Don S. or someone else who owns/breeds them.