• *The discussion of the creation, fabrication, or modification of airgun moderators is prohibited. The discussion of any "adapters" used to convert an airgun moderator to a firearm silencer will result in immediate termination of the account.*

MK2 shroud

Can you post a couple pictures? There was a time when FX was making modular moderators. The base unit is hollow, and then you could thread additional sections. There are a couple dealers selling cones that fit inside the main tube. But its surprising how well the hollow units work without the cones.
And I think there are one or two guys here that are set up to 3D print cones.
 
I have one of the FX aftermarket harmonic shrouds and it has what appears to be an air stripper on the front. I didn't find it of much use until I received a RAW 1000x 22 without anything that was anything but backyard quite. I put the FX shroud on and found a silicone plug to plug the backend. That made a huge difference in the bang. And with a Sumo it is very quite.
I haven't taken the shroud apart to see what is actually inside the front but it is more than a threaded adapter. I have taken the weight off the end, never saw that it did much for me.