Hello and welcome to YT!!! How tiny is tiny that your looking for? Most Yorkies are small, 5-7lbs and thats pretty small. I would never recomend a yorkie under 5lbs, trust me, I have one and I'm constantly worrying about her.
Believe it or not, but finding a Yorkie for under $400 will be hard, specially if you want it to be in great health, but that does not mean it's impossible either, when I set out to find my 1st baby, she was $475, so it can be done, just have to be patient and keep your eyes and ears open. You came to the right plave though and I wish you lots of luck!
also try the classifieds on
www.petfinder.com