Limited excess to a gunsmith with non-tox shot capability for waterfowl hunting, I'd go with an 12 gauge Italian over/under, set choked at modified and full, a Beretta maybe, better yet a Perazzi, steel rated and without screw-in chokes being able to shoot slugs for big game. The ultimate in dependability and durability. And with a 12 gauge I could go to any shop and find shells.
I would take my Ruger Red Label but a dependability issue may surface.
All the best