https://www.etsy.com/ has a lot of handmade items for small dogs. Some you can have custom made for your dog's size. Some are quite reasonably priced.
Usually most department stores and pet stores have a different idea of what "small" is but sometimes they do have things sized for puppies.
There are a few members here that make dog clothing. Did you look in the "Yorkie products for sale" area here on YT? Sometimes you can find a good deal on items that people's dogs have outgrown.