Does the switch that's in there now feel like it's pushing something? I suspect all those switches are really skinny, and they're all activating small switches that are all part of the same circuit board. Which means if you had the PCB diagram, you could potentially solder on some new leads to it, and run those to a relay to then turn whateveritis you want to turn on. Or solder on another switch, then run leads from it. But my next step would be to tear into the dash and confirm that that switch is just pushing on a PCB switch (100 style) and that it's likely more or less impossible that you could run a separate wire harness to it (60/80 style).
82 fj40, 99 uzj100, 06 gx470
97 DR650, 05 525EXC, 01 XT225, 89 TW200, 09 TTR125, 07 TTR90, 07 CRF50