Try the YTCA website. They are the mother club for the Yorkshire Terrier and they have a breeder referral list. It will take time and research on your part to weed through the bad breeders (I hope there are no scammers there) but if you do your part and not rush into a purchase it will be well worth it. Good luck! I hope you find your perfect forever furry friend.
I forgot to add, DO NOT BUY FROM A WEBSITE! You don't know what you are getting if you do that. Will the puppy be healthy? Will it be what they said it will be? There are so many horror stories on YT alone....
Buy local, meet the breeder, the parents of your puppy, and find out what health testing was done to help make sure your pup will be healthy. Like I said, it will take a while, but it will all be worth it.