Hello. Thanks for writing in. I am not sure if there are really any vets who specialize in Yorkies. Certainly, you want a vet that deals with small animals (cats and dogs) exclusively. The best place to go is localvets.com to look for a vet in your area. Call around and see how long they have been practicing and if they deal with a lot of small dogs. Most of your small animal practioners are going to have a lot of experience with yorkies and other small dogs. The thing to do is to make an appointment with a few of them for an exam and treat it like an interview. Decide who you like best. See if your breeder knows of any other breeders in the area or do a search online for yorkie breeders in your area and call to ask them where they take their dogs too.
Please let me know if you have any other questions. Hope this helps.