I have an addiction to .410 SxS guns.
I have a couple Huglu SxS .410 shotguns; one SST and one DT:
Bought both new. Maker's choke claims were nonsense, both guns were choked full/fuller. After having Colonial Arms cut them for choke tubes they have been a lot of fun.
Another venue, if you don't mind buying used, would be Spanish SxS .410 off Gun Broker or Gun Auction. Here are some examples I've picked up:
These can generally be had for under $500, condition ranging from VG to EX.
Or you can go whole hog, pick up a used gun in Spain, have it restored, and stocked to your measure:
Whichever way you go, be careful. The darn things are addictive.