I'd start with the corgi clubs associated with the AKC:
Pembroke and
Cardigan. It's not a guarantee of a perfectly ethical breeder doing everything 100% right, but it's much more likely. A good breeder will be prioritizing the health and temperament of the dogs they breed by testing the parents for diseases and genetic disorders they not only might have, but might be able to pass onto their offspring. They'll also typically participate in some kind of dog activity - showing is a big one, but also sports like agility or activities like being therapy dogs that visit hospitals. These are all signs that the parents are physically and mentally sound dogs (again, not a guarantee, but it helps) and that the breeder cares about the dogs they own and produce and breed as a whole, not just the money they can make from puppies.
You may have to be on a waiting list, and a good breeder will ask you questions to determine that you're a good home for their puppies (again, they care about their puppies and don't want them ending up in the shelter system!), but you get much more for your money - and probably at a considerably cheaper price, in my experience.