ive got the same buttons, if you look at your top pic, you will see a bit of white plastic. If you push this into the side of the switch body, then you can pull the round switch section out of the square body.

Once you have done this, you will find there is a round plastic ring that will unscrew. So you can drill a hole in the panel feed the button through from the front, fit the locking ring and then push the square switch part back on the the back (note its keyed)

Hope that makes some scene.

Trev