'iProtec' makes great lights & lasers kits that will easily clamp onto your barrel, I've got their light-laser combo on several of my shotguns, available thru Buds and Academy Sports, Etc. (iProtec Shotgun)..

Sean if your MPX12 has the bottom picatinny rail then any standard laser or lights can be added. A shotgun stock shell band for extra rounds as well (just click the picture here) : reddit.com/r/gundeals/comments/a031qf/shotgun_want_a_cheap_shotgun_emperor_firearms/