It would be perfectly legal to make your own version of one today. You could make your own or you could buy one already made. It is an NFA weapon and you would be required to register it and pay the transfer tax on it. The law making it illegal to manufacture new machineguns for the general public does not include other NFA weapons: you can still manufacture new short barreled shotguns, short barreled rifles, AOWs, suppressors............. Just not new machineguns.
There was a pretty good article on the Ithaca Auto Burgler within the last year in the Small Arms Review magazine. I have it around here some place if someone is really interested.
I notice on that link posted a couple posts above mine that they now come with 3" chambers and auto ejectors. Mine also has a 3" chamber.
FWIW: I STRONGLY advise you against firing 3" shells in one of these short shotguns. Don't say I didn't warn you.
Notice that the Auto Burgler has a pistol grip that is at pretty much a right angle to the barrels while those ones shown on the link above as well as mine in the picture below have a very rounded grip that allows the gun to roll upward in recoil rather than straight back against your elbow joint.
I have a
modern day version of it, manufactured by Serbu: