Ah Atlantic Arms, distributor of fine weapons reasonably priced, re-branded surplus weapons. One of their latest creations is the M92, which is much like the pistol version of the AK but with a stabilizing arm brace that bears a remarkable resemblance to a shoulder stock. This weapon is by no means a short barreled rifle; it is pistol [makes winking gesture]. Checking out this sub par marketing video:
The M92 retails for about $700 from Atlantic Firearms, which includes the stock arm brace. That price is kind of a lot for a cool toy, and I wouldn't recommend this be your first choice for a zombie defense weapon. You can make this California legal by jumping through a few hoops to have it transferred as a single shot pistol. I'm not sure if Atlantic Firearms can do that for you, but there are a few FFLs out there who will. Check out Atlantic Firearms for more info.