You might try Lee Hadaway, if he's still working -
http://thearmsroom.com/index.html. Haven't heard from him for several years and don't know his status.
Or J. D. Mcguire at
http://www.aiptactical.com/
Keep in mind the status of the firearms industry across the board right now (as in "swamped"). That includes shotguns too... maybe not as bad as ARs, but the small shops are pretty busy.