Welcome to YT! Your little yorkie sounds wonderful. I would love to have a therapy dog too but morgan gets so excited to meet people that she can't sit still when people approach.
There are a few great breeders on this site and there are also a few not so great breeders. Please remember that just because they are here doesn't mean the breeders are reputable or the yorkies are standard. Check out
Yorkshire Terrier Club of America for breeders in your area first and make sure you research the heck out of the breeder. remember, you buy your breeder first, then the puppy. If you check the library here you will find some good threads about purchasing a puppy and what to look for. YT is filled with great information. Good luck on your search!
Oh also we have members here that are a part of yorkie rescues. They have many great yorkies of all ages that are looking for their permanent homes.