I just acquired a pair of LED bulb replacements for interior cabin lights. They are meant to stick to a flat surface inside the lamp fixture using double sticky tape (good for the circular fixtures often found in the main cabin, for example). They do not plug directly into a light socket, but for $2 you can buy an adapter that does.
My bulbs came from www.sailorssolutions.com
. I have not yet tried them on the boat, only at home with a 12V power supply, but the light color has a definite yellow tone. They are not the usual blue-white you might expect.
These bulbs appear to have the light output of a 30W bulb but draw only 0.2A .
I have looked at LED replacements for masthead lights, where RF interference might really be a problem, and the vendor claims there is none, for what that is worth.
The nav lights I have seen are complete fixtures, not bulb replacements, so some hull mods might be required.