I had a couple of my square bridge Mausers up at Steve Bertrams shop. My Kurz is missing the button so we knocked around the idea of replicating one and I think he may have taken measurements. Never did the project so you would have to contact him to find out if he did.
The buttons are very standardised - the one from my TypeG fits the Kurz and fit another TypeB we tried as well.

The gun pictured above may have had its bolt release replaced at some time. Usually, the guns with this type of scope release have a divot taken out of the rear of the knurled surface on the bolt release to allow for the removal of the button. That is easily replicated as well.