There are several breeder members here for Biewers. It is wise that you are considering a retired show dog, but how about a rescue?
www.petfinder.com is one site where rescues list their dogs.
It is my understanding that Biewers are susceptible to all of the same health problems that Yorkies are. So having emergency funds to cover unanticipated health care costs is highly advisable. Also pet insurance.
Good luck with your search. also Welcome to YT. There is a search function here, if you type in Biewers you will find some threads here.