Pay attention to what Kahr tells you in that link:
"Thompson Short Barrel Rifles must be shipped to a Class 2 manufacturer or Class 3 dealer directly from our factory in Worcester, MA. The transfer paperwork between Kahr Arms/Auto-Ordnance and the dealer, known as a Form 3, must be completed and approved by the NFA branch, Bureau of Alcohol, Tobacco and Firearms (BATF) before the Thompson SBR can be shipped to the dealer. The customer needs to pay a $200 transfer fee directly to the BATF. Your local dealer can assist you in this process.
Some states do not allow the purchase and transfer of SBRs (Short-Barrel Rifles). Please check the state laws in your state regarding ownership of Short Barrel Rifles. A list of Class 2 manufacturers and Class 3 dealers can be found at the following website:
www.subguns.com. "
Ignore all the erroneous information posted in this thread!
You might find a Class 3 dealer listed with GunBroker:
http://www.gunbroker.com/User/DealerNetwork.asp
Also, have you handled a Thompson before? I haven't fired one, but for a .45 it's a heavy mother! If I were buying a short-barreled rifle chambered for a pistol round, I'd be looking at some of your lighter options. Of course, if I were to get a SBR, it would probably be in a rifle round -- something like a Krinkov.