This adapter is available for about $250 from the UK, but it only works on .30 Cal Luger barrels.
This is what Mark McWillis' opinion of this concept (
www.trosusa.com) said in an email:
"No I don't make anything like that and they're a BAD idea. They depend on the OD of the barrel being concentric with the bore. I have threaded thousands of barrels and that is almost NEVER the case."
If they were not so expensive, I might try one of these adapters. Now, the thread is likely 1/2 - 20, and US suppressors for 9mm are usually 1/2-28, so a second adapter is likely needed. I also think that these adapters were made by the Swiss by the same folks who made the Luger flash suppressor currently for sale on eBay
http://www.ebay.com/itm/Luger-Swiss-...item20e3fedba1