Pemi Fish and Game in Holderness was supposed to have a 2-gun match in September, but the club's competitions have all been shut down since March. I'm not aware of any club in Maine that has 2-gun. Western Maine Fish and Game Association has what they call "3-2-1 Gun", but that's not the same thing as say InRange-style 2-gun.
The best club in New England for 2-gun is Townsend Rod and Gun in Mass.