Dear Froggie,
I have a Behlert sight on my Model 57. I bought it directly from Austin Behlert’s smithy in the late 70s or early 80s. I do not believe that these sights are still manufactured. Austin Behlert was a contributor to the pistolsmith website and he passed away in 2005. In some of the threads on that site people asked him if he had any sights left over that he would part with.

Sincerely,

1chessiefan