I see, you might be able to squeeze in a dome/membrane momentary, like in a TV remote, but a latching on/off takes significantly more depth.
Could you drill out the space behind the "dummy" switch? Very doubtful, you would have to cut traces and wire around the cut traces at least on this side, and I don't remember what's on the other side...
So, as I work in the electronics industry, you would put a momentary switch there, and separate electronics to latch a relay on and off..
A lot of work... perhaps buying the switch assembly for a car that has the switch, but it would be expensive of course, and you STILL would have to add electronics.
Greg