Here's a link to the official AKC parent club for the Cavalier. There's a nationwide breeders' list on the menu to the left.
http://www.ackcsc.org/
One tip, and xsmommy can confirm this. Try to purchase a pup from a breeder who screens his or her breeding stock for inherited defects/disease. In addition, don't be surprised if the breeder interviews you. You are, after all, buying a pup in which the breeder should have much emotional investment.
Good luck, Cavaliers are delightful dogs. They are the most popular Toy breed in Great Britain for good reason.
i totally agree. She did interview me, we were on the phone for a long time just chatting and i believe that she does attempt to breed out the heart defects.