My suggestion is to order or build an AK with no butt stock, no pistol grip fore end, and a 16" barrel. Being under 26" and not a NFA device, this will give you permanent pistol status by all laws. If however you come up with a stock system that can pop on and off easily, you'll have the ability to carry a full blown rifle with you, maintaining pistol status the whole way until you pop the stock on.
Other guns you can do this with are MAC's, Uzi's, and Ruger Chargers. I am sure there must be others, but I don't of any off the top of my head.