The Yorkshire Terrier Club of America has a page of breeder referrals. After you get their names from the referral list, many have websites where you can check into their breeding programs more thoroughly. They don't sell through their sites, and you will need to call them if you are interested in adopting one of their dog. Remember show breeders sell mostly to people wanting a pet, not people wanting to breed, so they will be selling with limited registration, and this is a good thing. I wouldn't bother e-mailing they get hundreds of e-mails daily and if you are really interested call. You should know that they will be interviewing you, as well as you interviewing them. Best of luck.
Yorkshire Terrier Club of America About The Club