I found it extremely hard to drill perfectly positioned holes without a drill press. Since I already have access to a 3D printer. Designing a mount with Fusion 360 only took me 10 minutes, printing it took 4 hours, but I don’t have to man it while it print. I found it much easier and there is no risk of damaging the switch in the process.
You take the cover off the switch and pull the wires to the side before you drill it. Use tape if it makes you more comfortable.
You needed to take the cover off to access inside the box anyway.
If you measure where the holes should go, you just need to indent the plastic with a small phillips head screwdriver or just use some masking tape and mark the place for the holes with a pen or pencil. Then you can drill a tiny pilot hole and increase in size with larger bits. until you have what you need. If you start with a very small drill bit, it is very easy to stay centered where you want to be. If the holes are slightly out of perfection, just drill the holes a bit oversized and use a washer and tighten it perfectly straight.
There is no need for a drill press. The plastic is very thin. Drilling at an angle doesn't matter especially if you are a tiny bit oversized.
That whole operation should take less than 5 minutes.
However, I understand this is entirely a comfort zone issue, so kudos for finding a solution you are comfortable with!
Here is a little tool that you might even want for your 3D printed parts if it turns out you need a larger hole than you gave it.
It makes very short work of plastic and you can even just push it into plastic and start turning it to make a hole.
A tool like would let anyone make two small 4 or 5mm holes in a heartbeat.
www.thingiverse.com
