RSOV.com has in stock an A.C.M. full metal light weight M203 gas grenade launcher (XM203 - Short) which can be made to fit 40mm M203 gas grenades the standard available in the market. This doesn't have a trigger as compared to the regular M203 launcher and can easily be mounted under rail in the front. You can have this for US$41.99, the gun and the gas grenade in the photo are not included.