For $100, you can get a Polychoke that screws into your barrel (pump and auto shooters only of course). They still work.

A Polychoke has about 9 settings, from Full + to spreader, and you can dink with it and whatever ammo you happen to have until you get the pattern you want. then leave it alone until you change ammo, game, or whatever.

Not pretty, to most, but we're talking duck huntin' here.