If you trust Solarforce's switches, the rest of their product is just an aluminum tube. Here's the build I'm considering for my cheap-bastard's rifle light:
Solarforce LM-1 quick detach mount
Solarforce L2M body host (you need to bring your own LED module)
Solarforce PTS3 third-generation tape switch with replaceable - and redundant - switches
Stainless steel bezel ring - optional. Does the glint of bare stainless defeat stealth more than it protects your light from impact? I dunno, but I like having steel on the impact areas of my flashlights. The mild crenelations on this model provide a little bit of standoff from the lens, without narrowing the spill angle too much. You may prefer
a flatter ring if you want the wide-angle spillbeam for room clearing without using
a diffuser (which I recommend, if you're worried about very close ranges - and for any utility light)
Now for the electronics package without which this thing is just an expensive decoration, there is nothing better than
the Malkoff Devices M61. It can be powered with
rechargeable IMR batteries if you're careful and mindful of the dangers of working with lithium ion rechargeables; these cells don't explode and don't require fragile, recoil-sensitive circuit boards to maintain their safety. If you want it to just work, I recommend Surefire's CR123 disposable batteries - cheap, safe, and high capacity. They will run the M61 for two hours at 240 lumens, and they have a shelf life of a decade.
It's not quite a Surefire, but in some ways it is significantly better - brighter, better runtime, and the Malkoff modules are recoil hardened with large amounts of epoxy fill.
If monthly budget is a problem, you can substitute a cheaper LED module this month, or a Surefire incandescent lamp if you have one kicking around, and buy the good LED module next month; with Surefires or similar turnkey options, it's a large up-front lump cost which seems to be what you're trying to avoid.
