2104 390FL Berkshire - I recently added a blue LED to my existing plexiglass stair grab handle. The project was fairly simple since it was already prewired.
To find the LED bulb search on Ebay for "RV Replacement 86430 LED"
To install remove the 4 bottom bracket screws and verify you can see the wires inside the chassis opening. Installation requires you cut the existing wires end connectors and using 2 small wire nuts attach the new LED. The LED will fit flush pointing up into the clear section of the grab handle.
So is it turned on with the outside light switch. I have the same handle and have read that a lot of these handles are wired for power and i would steal you're ideal.
Our 2020 40E is already working from the factory. You can’t see it from a distance because the adjacent Berkshire emblem light is so bright. Operated by the external switch.