This is an expansion on a previous post of mine (https://www.thingiverse.com/thing:3880609), but I figured it was just different enough that it should be it's own separate component.

Here are the parts for integrating a power switch into the casing through the holes that were used for the XBOX button and two other buttons at the top of the case.

I've listed the parts you'll need in a subsection. You also need a soldering setup to connect the button to the wires, and you'll need a deburring tool to remove the tab from the inside of the hole in the switch cover base plate (USE GOGGLES AND GLOVES AND DON'T TOUCH YOUR EYES.