I’ve looked for suitable LED bulbs but never found any, have you a source you can recommend?
The above would be a good place to start though they are quite expensive. Alternatively, there are lots on ebay (most 12V LED bulbs will run reasonable ok in 6V systems) that can be modified to fit if you are handy with a soldering iron. I am a big fan of LED bulbs. It saved us having to upgrade the battery in our motorhome as the LED lights I installed use minimal current. As said before, the lights on my Honda used to go out at tickover (they are fed direct from alternator not via battery). Now they stay on at tickover and are MUCH brighter.