I was trying to mount a keystone jack in a unique location using a typical single gang US electrical cover, and it was much too large to fit in the space. I recreated the mounting mechanism and put it on a small disc. It holds the jack nicely within a minimal space and allows for a minimal hole and 2 mounting screws. Pretty much any other keystone style jack should fit, but I haven't tested.
The author hasn't provided the model origin yet.