How about using a rear heater switch from an 80.
Re-label it for batteries. Then put the two LEDs on the right and left sides of the switch windows. So now you have the LEDs for the monitor and a switch to control the dual batteries all in one?
Speski OffRoad LTD, Cargo Solutions for Toyota 4x4's http://www.SpeskiOffRoad.com
"80 series, with a fridge"
1976 FJ40, Project with little progress.
2004 Starcraft 10RT