Check the YTCA breeders:
Yorkshire Terrier Club of America About The Club
But also read this first:
http://www.yorkietalk.com/forums/yor...ead-first.html
Good luck on finding your Yorkie
Repsonsible breeders will have had all the testing done. AKC is more reputable than CKC (Continental Kennel Club).
Ask lots of questions of a breeder before making decisions, a good breeder will not mind questions. Remember this is a decision that will last for many years so don't make it in haste. if you are not sure about a particular breeder you can always ask members here.
Also check out this section:
Breeder, Vet, & Groomer Reviews - YorkieTalk.com Forums - Yorkshire Terrier Community
I am so glad that you are keeping Nibbler.