Welcome to YT!
"Teacup" is actually not a recognized term for yorkies. All yorkies are toy dogs. There are a lot of great threads here about how to find a good breeder. Just look at the bottom of the page and you'll see an option to search this entire forum.
I am not sure where you live in Australia -- any chance you might want to get one from SE Asia?
There are plusses and minuses to having a very small dog. Mine is 4 lbs and I think he's perfect, but many people can tell you why having a larger yorkie is great too. A lot of people say the smaller dogs aren't as healthy, but I don't think that's necessarily true, just make sure you find a good breeder.