Hello and welcome....I'm glad your aware of the many issues when it comes to the purchase of a pup. If you go to this section there's some stickies at the top of the page with some helpful tips.
Yorkies For Sale or Wanted - YorkieTalk.com Forums - Yorkshire Terrier Community
One of the places you can try contacting a breeder through is the Yorkshire Terrier Club of America and see if they have any upcoming litters. You will still have to be careful this is no guarantee of not having problems. Take your time and ask a lot of questions. Good luck in your search.
Dog Breeders Map List- The Yorkshire Terrier Club of America