Hi there, as for a tiny I think you may just have to see if someone has one by default ,as in thier litter has a really small pup in it. Get to know a good reputable breeder and they may let you know when such a little pup comes along but there id no guarantee that they will stay extra small and you may have a long wait , but dont set your heart on a certain size.
I have had yorkies of all sizes and loved each and everyone for their character not their size.
You could always try the rescue sites in the UK I have seen some really adorable yorkies on there of all sizes including tiny ones.
__________________  From Julie  Alfie & Lottie  |