Are you willing to travel for a tactical shotgun course?
Sig Academy offers a shotgun class held at their facility in Epping, NH, but otherwise the closest I've seen to this area is with Rob Haught through Grey Group Training held in Highview, WV, with (Gabe) Suarez International in Bellevue, MI, and with the US Training Center (Xe/Blackwater USA) in Moyock, NC. These classes are all being offered between now and Nov. 2011. There's also Gun for Hire with several locations throughout NJ. Check their respective websites for info.
I've trained at Moyock, NC back in 2006 when they were still Blackwater USA (Extreme Officer Survival and a CQB class) and their instruction and facility was awesome. I highly recommend a training class there if you ever have the opportunity. I've also trained at Thunder Ranch, Gunsite, and Valhalla Training Center in my former military days.
I'm also attending training classes this summer with REDBACK ONE (Jason Falla) through Grey Group to be held in Meriden, CT (2-day Tactical Carbine) and with ICE (Rob Pincus) for Combat Focus Shooting/Advanced Pistol Handling to be held in Westford, MA. Some top quality instructors make there rounds, you just gotta keep an eye out for their classes.
I'm sure there is likely more offerings closer to home, with more local (in New England) training cadre with whom I'm not familiar.