For a video I decided to make a camera-side mount for Leica L lenses – I did it in Fusion 360, so if you want, you can go and download the mount from here:

This is a directional mount — so the top, as viewed from Fusion 360, is the top of the camera. I don’t have a lens release for on it since I didn’t need one for the project I’m working on, but it’s not too hard to add one. If you wanted to repurpose this to make a lens cap, you would want to duplicate the “nub” that’s on the left side all around; that way it could go on in any orientation.