BTW, while the OP specified AA battery flashlights, if you don't mind USB rechargeables, this lightweight little thing costs $12-$25, depending on the vendor, and would make a fine pocket flashlight with the rubber handlebar strap removed (it's screwed on). It weighs almost nothing, is bright (although not the claimed 300 lumens -- I'd guess closer to 75-100), reliable and lasts as long per charge/mode as the manufacturer claims.

The beam is unusual -- it's a roughly trapezoidal pattern, not circular, because it uses a curved mirror reflector that emulates the Busch and Mueller bike lights. It's intended to spread the beam to appear roughly equal in intensity from near to far when aimed appropriately -- but will appear unusually irregular when aimed directly down up close. But it offers better side visibility than any other bike headlight or flashlight I've seen.