I always recommend the YTCA, it's the mother club for Yorkies and there usually is a breeder in most states. These breeders breed to standard and don't breed to suit the public latest buying whims. You still need to visit the breeders home in person. If you buy from a good breeder, she'll be able to help you with you pup for the rest of it's life and she can also help you decide if a Yorkie is right for you.
Dog Breeders Map List- The Yorkshire Terrier Club of America