Pilot light device with
If I am reading your question right what you are looking for is a jewel light, which you won't find in a big box retail store but you should be able to find on line. This is an image of a red jewel light.



If that seems a little more than you want to handle, you might try and install a switch with a lighted handle and buy a wall switch blank for the other slot.



These can be found in some big box hardware stores, usually in white. If not then you can also order these on line.

Good luck.