I just stumbled across this product, seems like a clever idea. Basically a hockey-puck sized set of waterproof LED running lights - usable either as Red-Green-White, or just the Red-Green components. Might be a good choice for a small runabout, or backup lights for a bigger boat if they're bright enough. I have a masthead LED tri-color, but the backup ones mounted on the pulpit haven't worked for years and I've been lazy about keeping them going. If bright enough this might be a better backup.

According to the manufacturer the all-around white version is USCG approved, but they don't say anything about the R-G version. That might be a small fly in the ointment.(edit) I can't seem to find where I read about the USCG approval, but did see it on one of the vendor websites when I was looking around yesterday

Pyachts seems to have the best price, at $49 + $20 for a rail mount. I have no connections with any of these companies.

FWIW
Max