Define inexpensive? Define how much you feel you will have to rely on the light.. Lights are kinda like optics. Most do the same basic thing, but the higher the price (and the more reputable the manufacturer) generally the better and more reliable the light (and optic) will be. Candlepower forums has a head jarring amount of information that stretches beyond "Hey SureFire rules" or 100 lumens isn't enough..

A good reliable and common configuration is as noted previously, the SureFire G2LED with any number of 1" mounts. The G2 is more or less an industry standard both for quality, reliability and form factor. There are good reasons for that. I"m not bashing Fenix, Streamlight, Olight or any number of the other fantastic manufacturers out there.. the G2 is just a good starting place.