There was a WCIF at Sims Cave for a missile launcher and since I haven't seen any around I offered to convert this one from Fallout New Vegas. Also included is a missile.
Both are decorative items and can be found in Electronics -> Misc (because the Deco section is plenty cluttered already) and both cost $150. The polycount for the launcher is upwards of 6k so use sparingly. The missile is much lower.
I tried to scale these appropriately so if you use an OMSP you will find they are sized to rest on a sim's shoulder, like how the launcher is positioned on the player character in the original games.