I was searching for simple brackets for my led power supply but couldn't find what I wanted. The brackets have slots for M3 socket cap screws (you need 2 brackets for the 4 tapped screw holes at the underside of your power supply). The tapped holes on my power supply are 85 mm apart.

Print @ 0.3 layer height (important!) and 20% infill (not important). Be aware that there is some bridging required for the counter sunk screw holes. EDIT: I made a change to the design so it is easier to print the countersunk holes (added one 0.3mm support layer).

Attribution - Creative Commons

powersupply, mounting, bracket