I see two YTCA breeders in New Hampshire and 4 in Massachusetts. They may not always have puppies all the time, but reputable breeders have fewer litters than puppy mill breeders so sometimes you do have to wait. I am so glad you want to find a quality breeder. Perhaps you could interview some and see what they suggest. Here's a link:
Yorkshire Terrier Club of America About The Club. I personaly would be worried about buying from a breeder that I haven't met, and checked out throughly. Good luck with your search.