You could also go with the not as stock approach.
I recently finished installing my backup camera system that is initiated via a switch.
Like you, I wanted to use the switch bank since I only have the ESP and Hazard buttons.
The problem that I ran into is that the circuit board overhangs much of the bay:
The $3 switch I got at radio shack is deep enough that the prongs would interfere with the board (could not find a shallower switch) if I put it in the leftmost location (preferred). So I had to put the switch in the rightmost bay since the board stops.
Here is a picture with it installed:
A note to anyone who does something like this: the button is just barely non-symmetrical. Be sure to double check that you are drilling through the correct "bay" of the button. If you do put the hole in the wrong side you can get it to fit however. It just won't follow the contour exactly anymore. :doh: (I felt like an idiot when I realized I drilled the wrong side)