I did it with some of these. Wasn’t too bad. It’s only for the LEDs.

https://www.amazon.com/ELEGOO-Prototype-Soldering-Compatible-Arduino/dp/B072Z7Y19F/ref=mp_s_a_1_2_sspa?keywords=circuit+board&qid=1640475465&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQTI2TDBKTjc3QlBNJmVuY3J5cHRlZElkPUEwNjE5OTMxMU84UlZSUEdXQVlCRSZlbmNyeXB0ZWRBZElkPUEwNDM1MzEzMUVZWVNQMlo0N0dMJndpZGdldE5hbWU9c3BfcGhvbmVfc2VhcmNoX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

https://www.mouser.com/ has everything you need if you're in the US. Tons of buttons and switches in whatever size you need. Most of the products have links to the spec sheets too, which will tell you what size and type of cap to use. They also sell the caps.

I've found an easy way to mount them is to use protoboard. Something like https://www.amazon.com/gp/product/B072Z7Y19F/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

You can mount that with glue, screws or whatever to the inside of your box. You can push the button pins through the holes and solder them from the back.

Here's how I've done it in the past. https://i.imgur.com/Pekg2DL.jpg

The green board isn't part of the circuit outside of the pins themselves, so you can mount it anyway you want, including driving a screw straight through it.