One of the rules of the Yorkshire Terrier Club of America, CODE OF ETHICS
http://ytca.org/ethics.html
"shall not use terms as “teacup”, “tiny specialists”, doll faced, or similar terminology."
So if you see those words on a website you can be sure that the yorkie your buying hasn't been health screened. For a list of ethical breeders see this list.
http://www.ytca.org/breeder4.html
What you're looking for is a yorkie with shorter muzzle, and just make sure you see the parents, don't trust pictures only.