There has been some mention here recently of a German E-bay seller, Franksmusic. It might be of interest to some here that he also sells rather nice flattop bridges of various designs for very little money. I bought an ebony bridge with bone insert. As shipped, they're about 14mm high, with a 50mm wide bone insert. I've used it for a bouzouki, where it's just fine. For a bowlback, these may also work, but the design may be a bit chunky. Frank told me that he has them made specifically to his specs, so maybe he can help with getting more bowlback appropriate ones as well.