1: Maglite makes a LED drop-in for people who want to upgrade their old incandescent flashlights. The drop-in is slightly larger than a standard PR-6 bulb since it was designed specifically to fit the socket in a Maglite. It doesn't fit 100% of flashlights.
This actually works very well in a Fulton.
It's a tight fit at first, but with a little persistence, it'll just snap into place and stay put. You might have to fiddle with its rotational position to make a good positive contact, or even put a bead of solder on the end of the LED modual, but it works, I've done it.
In Canada, they sold the Mag Led at any "Canadian Tire" a hardware store chain we have here, that is common. So it is easy to get a Magled whereas everything else would be special order.
Anything more advanced then that, you'd have to ask one of the Ledheads, I'm an incan guy. I'll tell you to drop an HPR44 and a couple of 26650 Lifepo4 cells in there.
The 3rd one is Mag-Led loaded. I can post more pics of it if you want.