[моё] Finally attached the button to the power supply unit that I've wanted for a long time

Initially I made the button on a wire (unfortunately no photo, but it looked decent), but it turned out that the board has a diode bridge for a single‑pole button, so here only a double‑pole one is needed.
But I was kind of clueless and thought that such [buttons] don’t exist due to the form factor, but it turns out they do.

Assembled, of course, it doesn’t look great, since I experimented on how best to make a hole in the case for the button, and it turned out not very pretty, but I actually don’t care, the main thing is functionality.

In my opinion, the best way is to mark the spot for the button and drill, then trim with a craft knife.

The best way is to 3D print your own custom case.

well, first you need to buy it, then design it, I dunno, I dunno

Here, putting a paw on the heart, the most basic printers for basic materials (including the materials themselves) cost next to nothing. Learning to model in the same CAD applications is also not a trivial task. But if you really work with electronics, where custom enclosures are needed, it will come in handy more than once.

I basically have the cheapest (entry-level) 3D printer at home. I have printed so many models for painting on it that I can't even count.