This is a box for a Gardner Bender GSW-41 switch that will mount to the AnyCubic i3 Mega. It mounts by clipping in to the hole for the voltage switch to switch between 110/220 volts. I figured most people set that switch once, and never use it again anyhow, and there is enough room to run wires in the gap between the outer case and the power supply.
I use it to switch my custom LED lighting on and off. I wanted to be able to run custom wiring in to the case so I could power the LED strip off the internal power supply, and it was in a convenient spot. I also didn't want to have to drill any holes or make any non-reversible customizations to my printer.
This box originally had a bottom to it, but in the end I decided to leave it with an open bottom for several reasons. 1) it makes the supports easier to remove, 2) you can't see the bottom anyhow when it is installed, 3) less material, 4) access to switch wiring if needed, and 5) the option to run wires out the bottom if desired.
I actually ended up running the wires that go out to the LED strip through the bottom of the box. You can see the ugly yellow wires in my picture. If you choose to run the wires this way, it can be made to look nicer with a small chunk of black wire loom (which is what I plan to do). Because my LED strip is stuck to my Z axis with adhesive, I also plan on putting in a couple bullet connectors behind the front of the Z axis where you can't see them so that I can easily disconnect the wiring in the event I want to remove the Z axis.
Please note that this is technically an AC switch. I didn't find a DC rating on it, so it may not be appropriate for this use. I used it anyhow, but I make no guarantees about the safety or reliability. That's on you.
I purchased my switch at Canadian Tire. The item number is 052-6974-0, but the same switch seems to be available on Amazon and at several american retailers. I don't see why a totally different switch wouldn't work, as long as it is designed to fit the standard 0.55" (1.39 cm) x 1.125" (2.85 cm) cut-outs.