I bought one of these
But i also had one of those vent ribs to clip onto. Not sure if your slug barrel has that. It came in a pack of 2 or 4 for various models. Only one fit mine so i gave the others away to whoever's they fit. They are alright. I'm not a pro by any means I just wanted something cheap that fit the bill. I'm sure there are much better out there.
Seems they also have ones if it doesn't have the rib. You'd have to measure for fitment i guess.
But i cant give much of a review. Hope this helps. I'd def give Mossy a call and see what they say. Let me know cause i'll probably do the same. I'm lazy so i'll probably email them though.