Back in 2004 I bought some white LED bulbs from Superbright.
LED Lights & Accessories - SUPER BRIGHT LEDS
While they drew minimal current, about 80 mA., they weren't much brighter than a night light
. Recently I installed these 15 LED warm white units to replace the 921 incandescent bulbs that came with our trailer. While not cheap they should last a long time and I expect some pay back in battery
life. At 200 mA. they draw 1/7 the current as the 921. I always found the 921 a little too bright. These are perfect and the warm white is great for reading. To use the existing socket, I mounted them on a small piece of printed circuit board.
For the technically curious, the circuitry on the back is a full wave bridge to eliminate polarity issues followed by what I believe is a current source driver which maintains a constant brightness with variations in battery
For use in a camper, these are the best I've seen. Raz