Getting a particularly small Yorkie is a lot of work.You are also looking at the possibility of constant vet visits and naturally large expenses as a result. As a general rule, the "teacup"(which don't actually exist) yorkies are just the product of underfed parents. Or particularly small dogs, for whom it is actually dangerous to have a litter. If you really want a small Yorkie, just go to a breeder and pick the smallest one of the litter.
If you are interested, I am from Toronto, and I know a wonderful breeder in Grimsby. Here is her webside
www.braecliff.com. She is a lovely woman who is truely concerned about her dogs. She has also raised over 30 champions over the years.
Best of luck with finding your baby!