I was holding off until we had a picture from "darbyjudy," but figured since the recommendations had veered into using household 120V switches and add-on LEDs I'd pass along this info.
The OP's coach is a 2017, so I expect it would have a lighted water heater switch- one that would not require modification, rewiring, etc., just replacement if its lamp had failed. I mean, manufacturers are trying to save money on every component, but I'm hoping they didn't on this one.
The OP's coach may or may not use Sigma switches
and indicators on the "convenience center" (a.k.a., "monitor panel"). Here is a data sheet
on the "1 and 1U" switches. Sigma does not sell directly to retail customers.
I replaced my coach's Sigma switches and indicators with LED versions. They are drop-in compatible with the originals. I bought enough for all the switches/indicators, and will replace the bulb versions as they fail.
17880 Commerce Drive
Bristol, IN 46507
12V lighted (LED) swtch:
A1-31 SWITCH 12V BLACK W/RED ILLUM SPST ON/OFF 14/28V LED
1Z-03-U INDICATOR PANEL 14V BLACK W/RED ILLUMIN
I seem to remember I had to ask them to ship by least expensive method, as the default cost more. I could have them confused with another supplier, though.
They order these from the manufacturer (Sigma) once a week (or so), so you may find they take a while to get to you
Hopefully, the link above shows a switch that's compatible with "darbyjudy's" convenience center.