Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4549461.
I designed this as an alternative mount for the PSU while building a LACK enclosure for my Prusa i3 mk3. (It is designed for the silver PSU -- I'm not sure if it works for the black one or not).
I wanted to have the PSU outside the enclosure but I wanted it on the side rather than the back as in the original design. I also made it mount horizontally.
There are two parts: "top" is the larger part that holds the top of the PSU to the underside of the table; "bottom" is a small block that screws to the leg of the table and in turn the PSU screws to it (using the screw holes where the PSU normally attaches to the base of the printer frame.
I originally used this with the "v1" Prusa Enclosure, and when I switched to the v2 enclosure it still works just fine.