The slip on 15mm Weihrauch moderator is available at Chambers and they'll ship to the US. I just ordered another one before Christmas. I have a HW30 Urban Pro with the shortened barrel and glued on mod and also have another HW30 that I placed the HW slip on mod onto. The urban pro is quiet and the other one is just as quiet with the slip on mod installed but it really makes the rifle long. Another route to consider, adding to the above suggestions is, if you must add a mod, buy a 15mm to 1/2unf adapter and add a small mod to it. The 30 is pretty quiet to start with....