Just a heads up, I had the same problem in a PM and ended up having to host photos on ImgBB — Upload Image — Free Image Hosting then embed the photos (or you can just link to the photos).
I tried searching for a while to find that for my replacement mount and came up empty handed. Best I came up with is measuring from the rail to this line that is inside the ring (see pic). That measured 1.4985". So I went with the 1.5 Spuhr as a replacement.