I had a LH-360W power supply from an old 3D printer that I was using to power a battery charger. I decided to print a mounting box for it and add some binding posts and a power switch. I forgot to dimension the cutout for the power switch before I printed it, so I had to improvise. I have fixed that in the .stl now. It's 13x28mm. There is a small clamp for the power cord designed for two M2 screws. Length will depend on how thick your power cord is. The power supply has three M4 mounting holes.

I designed it to be able to be printed in one piece with no supports. You might have to clean out a hole or two for the screws or binding post, but that just makes for a good fit. Saves time and filament too. I used 3 walls and 15% infill (it's mostly solid) with .6mm nozzle and .24 layers. It prints upright and I did use an inner brim to secure it to the plate. I printed in PETG-CF.