Hi, I have been looking for Biewer puppies myself. I found a breeder in Naples, Florida.
I live in NY, which is a little far for me. They list a boy, not a girl on their site
Here is their page on AKC site:
https://marketplace.akc.org/breeder/cougartown
This is the breeder's page:
https://cougartownkennel.com/biewer-terrier
maybe they have a litter coming up. Hope this helps