I used to own a Guest model 461 anchor light, a popular piece of gear when many of our good old boats were built. A fundamentally well-made device, the incandescent bulb suffered from poor light output and the special screw terminal 6-volt lantern batteries were expensive, difficult to find, and had a short lifespan. Carrying a spare 6-volt bulb that fit nothing else aboard was another minor annoyance. A reflection of my dissatisfaction with it, I left it aboard when I sold the boat with which it came. I suspect there are many of these buried deep in lockers or gathering dust on basement or garage shelves.
I recently picked up another one for a few bucks at a flea market hoping I could improve it with newer technology. I first replaced the old bulb with a 12-volt LED bulb. This particular one has 2 LED’s on all 4 sides and one on top, giving 360 degree illumination. I bought a pair of these bulbs on eBay for 75 cents. While there, I also bought a cassette to hold 8 AA batteries for under $2.00.
I cut off the lantern’s ring terminals and soldered and shrink-wrapped the cassette wires to the bulb socket, checking polarity. (Strangely, it was black to white and red to black.) I loaded the cassette with cheapo carbon/zinc AA batteries from Dollar Tree (8 for a buck) as a minimum performance test. After running continuously for a week, the light is dimmer, but still shining. I am sure alkaline batteries would function much better. I filled the excess space in the lantern battery compartment with pieces of pool noodle foam to secure the cassette against movement.
While not USCG approved as an official anchor light, I have modernized this device for less than the cost of an original battery.