I kept out some of the live feeders to use as breeders. I got them from the local reptile store, and from a local rat supplier.
I wouldn't bother with the rat rescues, and the people adopting them out. Their aim is rats as pets, not producers. You wouldn't give someone a pair of puppy dogs to breed and sell the pups as food to the asian market. They feel the same about the rats.
Good luck, and make sure the rats looks healthy without sneezing, without runny eyes and not skinny.
Good luck!