So glad you asked this!
I'd recommend checking out the Library here on YT:
Breeding and Breed-Specific Library - YorkieTalk.com Forums - Yorkshire Terrier Community
It's a great place to start as well as checking with your local YTCA group (Yorkshire Terrier Club of America).
Good luck in your search & welcome to Yorkietalk!
(If you need a hand, don't hesitate to ask
)