Actually easy to find, and totally legal. Try American Gun Craft, they ARE online, and have several versions of the 12 ga. double barrel pistol. They will affirm that the pistol is legal; BATF&E agrees. I'd fire mine, but 209 primers are impossible to find now. About to try some #11 caps!
I contacted the Diablo people about the possibility
that they might do a Howdah replica-- but they said
there were no plans for it. I think the look of the
hammers and the antique style is way prettier. The
American Guncrafter folks have a well reviewed quality
piece-- I would just prefer a not so modern looking arm.
The Howdah is a perfect all around short range companion
with the look and feel of an old time go to reliable.