It can be done, but.....
Posted yesterday and thread moved somewhere I can not find it. Anyhow is anyone aware of a red led drop-in for C/D maglite. Will use it fro scan light while hunting.
I went to my spare parts box, got a red Nite Ize LED, and a PR adapter manufactured for the tiny dual pins of those AA Maglite modules.
Bottom line: it works in my 2D Maglite, but there is a really ugly 'spot' which can't be adjusted. The little PR adapter would probably be hard to find these days, so you might substitute the new Xenon bulb holder by spreading the pins before inserting them. It'll still be an ugly and pretty dim spot, but one that ought to still operate. With a lightly frosted lens the 'ugly' might get better, but at the expense of an even weaker beam.
I believe I'd buy a regular LED bulb sized (lumen-wise) that'll be suitably bright after you've run it through a red lens filter.