My advice would be to go to a local dog show and speak with Yorkie breeders to find out more about the breed, puppy availability, and perhaps references to other reputable breeders you could contact. That's your best bet for a
healthy purebred Yorkie. In a litter, not every puppy is show quality, so the other non-show quality puppies are available to purchase. Or, sometimes breeders will allow their retired show dogs for purchase as well. Here is a list of upcoming shows you could possibly attend:
https://www.eventbrite.ca/d/ma--boston/dog-show/
Otherwise, yes, please do keep an eye out for puppies for adoption at your local shelter. That obviously would be an amazing think for you to do.