we found our breeder by word-of-mouth.  She and many others are listed in our local breed club, so that's a good place to start.  I think some decent area breeders may NOT be in the Cascade Pembroke Welsh Corgi Club, so, your local breed club may not be exhaustive, and some of the breeders in it may not be the best.

Just do your homework, talk to a lot of people.  Luck is when Preparation and Opportunity meet.

PS read various blogs for tips on spotting good/bad breeders.  Wendt Worth Corgis has a blog, also Joanna Kimball (Ruffly Speaking?).

A rescue or shelter animal is maybe more of an unknown, but I can say that many of the best dogs I see on my circuit are mutts from the pound.