Get from Amazon : http://www.amazon.com/gp/product/B003G2Q27Y?tag=wayofcats-20

NcStar Green Laser with Universal Barrel Mount/Pressure Switch (ARLSG)

Includes powered by 1 lithium type battery and coil pressure switch
532nm green laser beam
Universal rifle barrel mount bolts and shotgun barrels
Momentary and constant on off cap switch
Made from aluminum :