I've gone down a different route than
Nigel with these lamps. They were used in the heads and shower/wet locker and those were areas were I wanted red and white switchable lights.
So I've gutted them entirely, then installed a bright day white (my preference for heads/galley, rest of the boat is warm white) LED strip (2835 at 120/m density). Next to it a red one (actually a RGB one with only the red wired because I already had that around, but a plain red one would do just as well). Then wired both up to a on-off-on switch that exactly fit the cutout for the old on-off switch (RS Components #7410886). From there to two spade connectors on the back to match the existing connectors on the boat side.
Very pleased with the result so far. The Rensch diffusor does a great job of obscuring the fact that they are LED at all and being the original fixtures, they of course fit perfectly. I polished the chromed plastic (ugh) with some Peek metal polish so it shines again.
