Check out the Shih Tzu Club of America, and see if they have a list of member breeders. WELCOME! Official American Shih Tzu Club Website | American Shih Tzu Club
You can also contact Shih Tzu or all breed kennel clubs in your area to see if they keep a list of member breeders. I'm not sure what the current average price of a well bred Shih Tzu puppy is, but since they tend to have smaller sized litters, and good breeders don't constantly breed, any price that seems "too good to be true" probably is.
Your best options would be to get on a good breeder's waiting list, and be prepared to, well... wait. Everyone and their uncle is wanting a puppy these days. Alternatively, you can check out rescues, but again, they rarely have puppies come through, and you more than likely need to be pre-approved to get a puppy. Either way, the interview process will be a lot longer than "Do you have puppies, and how much are they?".