Inspired by JSAUX Modcase Vertical-Orientation Adapter by Sabrina. This was exactly what I was looking for, but Sabrina's design needs to be cleaned up, and the creator hasn't uploaded any CAD file, only an STL. So, I decided to design one from scratch myself.
I've also included a plain universal mount model, this can be stuck onto different accessories using a strong double-sided tape. It is identical to the JSAUX official 3D model, but with 2.1 millimeters shaved off the top.
The author remixed this model.
I combined my Universal Adapter design (remixed from the official ModCase 3D printed parts), with the central mount of the ModCase (from the mount design environment), at 90 degrees to each other.