Warthog Firearms can help with all your NFA needs. Forms 1's and Form 4's as well as the items themselves.
Brian and I use Crux Surpressors and our own flavor of lower for our short barrel and long range rifles.
To get a gun trust use this link http://199trust.com/#oid=1024_1, it takes about 24 hours and the cost is around $79.00.
Warthog can get:
Advanced Armament Corp Dead Air
Knights Armament Company Crux (some in stock)
Ruger (22lr) SCO
Surefire SIg Sauer