Many coaches of our vintage used mid 70's Chevy P/U headlight switches.
If you can get it out , Napa or AutoZone can match it.
If the shaft behind the knob is triangular , there is a spring loaded button on the switch opposite side from the wiring , that you push in to release the shaft , then the retaining screw in the dash can be removed.
As the shaft is removed the lights will come on so disconnecting the battery first is a good idea.
I have a picture of the switch somewhere if I can find it I'll re-post.