I'm in the same boat, and I've bought the streamlight polytac for about 35$
Supposedly holds up pretty well to even shotgun recoil as a WML with 130 lumens, 3 hrs of runtime, and takes CR123 batteries.
Gets pretty good reviews, too with dudes who run em hard. Might wanna check it out!
I'm looking at mounting options now, and wondering whether I should buy the scout mount which directly interfaces to the MOE handguards I have, or purchase a rail section to mount the magpul cantilevered light rail mount with the V rings...
Any advice? It's a lot more convenient to outright buy the light rail mount and rail section, than the scout, plus V ring mount seperate but I don't want to add another failure point if I can mount directly to the MOE handguards.