The old style barrels used to go to the UK for Venom to swage the extra stuff on the barrel, then back to California. That source is long gone. IIRC mine was made from 'the last of the barrels' a while back (ten years?). There were some options WRT barrel length, number of baffles and sights.
In the day Tim also did the same thing with QB and Condor barrels (I have one of each).
They still come up from time to time used, that's pronbably your best route if you don't want to have someone build the barrel/shroud up for you.