If you're talking about the EL shroud, the grip can be removed. It comes with the vertical grip or a small set screw that goes in it's place if the grip isn't used. I personally don't use the grip on mine.Does it have to come with that vert grip attached or is removable?
HKParts makes a pretty solid fake suppressor for the USC. It doesn't look like the AAC but it attaches securely. The shroud is fixed to the bottom rail and it secures in place via the bottom rail screws.
I see they are also selling one by MFI that looks similar to what you are looking for.