They are readily available. There are several dimensions/styles of low voltage switches as well. Do a google on "illuminated RV switch" and you'll find lots of them. If near a dealer or independent RV parts store, they can get you one.
One thing to know about an illuminated switch is that you'll need a 12 volt DC source that is always on. If all you have is two wires at the switch, you'll need to get another wire to the switch with power that is always on. The switch will have 3 terminals on the rear like in the photo.
