I very much want a trench gun, but if you don't have any a normal 1897 will do for me. The trench gun has the same barrel (20") as far as I know. The only difference was the bayonet lug and heat shield accessories from what I read. The ability to slam fire should be common to all of these shotguns as they traditionally lack a trigger disconnector.
Reproduction trench hardware is available in America. I have no idea if anyone can bring these in:
But like I said, if Marstar has factory trench guns coming soon, I will happily wait for those.