I am not sure if there is anyone on here, as I am not all that active, but the breeder from whom I purchased my Biewer (I live in Germany) is someone I would definitely recommend. She doesn't speak English all too well, but I could translate if you needed help, as I did all of my contact with her and the purchase contract in German. Her website is
Vom Weinberg - Biewer und Yorkshire-Terrier Zucht but its again all in German. I am not sure if she is expecting any litters soon, but you can probably email her in English and she will try to respond.