Mossberg 930 SPX comes with a short Picatinny rail. The rear sight is mounted to it. I have a Picatinny Riser that can mount on the rail, but there is no room left on the basic rail to mount the rear sight. I want to mount BOTH the riser and the rear sight on the rail so that I can put a reflex sight on the riser and still use the iron sights. The basic rail is a little more than 4 inches, which is too short. I need AT LEAST a six inch rail to mount to the Mossberg. 8 inches would be better. Does anyone know where I might find a six or eight inch long flat Picatinny Rail I could mount on the gun?