I don't think there's an actual switch there, per se. Not like a CDL switch you'd add to an 80, or a rear defroster switch you'd have on a 62 or 4Runner.. or even the switches left of your steering column. Those switches in the center are more like the buttons on the front of your DVD player- they're just depressing something else on the back side, that's soldered to a circuit board.
at least that's my best guess, based on the 10-15x I've had mine in my lap futzing with the stereo.
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 89 TW200, 09 TTR125, 07 TTR90, 07 CRF50