On Friday, April 19, 2013 4:58:05 AM UTC-4, wrote:
We now can buy 120V AC LED bulbs that will fit any household socket.
But do they make a similar bulb that uses LEDs, runs on 12V DC and
screws into a standard socket?

Aside from "screws into a standard socket", yes, there are tons of LED-based replacements for automotive bulbs on the market. Some better than others. A lot are garbage.

The ones that have the round dome shaped traditional LEDs are generally garbage. The ones that have LEDs that look like little square bits of clear plastic are the good ones.

Look to replace bulbs lumen-for-lumen. Less lumens means less light. I usually go for more lumens, for more light on less power.

With all the old incandescents turned on in my camper you could barely see and it drew several Amps. The LEDs I replaced them with have 16 high-intensity LEDs per panel, plugged right in place of the old "941" type bulbs. With them all on, you can perform surgery it's so well-lit, and all together they draw 2 Amps.