Phillip:
There's a nice show in Presque Isle, ME, run by the Presque Isle Fish and Game Club. http://www.pifg.org/
It's small and local compared to the other suggestions, but gets lots of attendees from northern Maine and New Brunswick. It's also the most fun/best run show in Maine, in the opinion of many of us who attend a lot of them.
Others in Maine include the Maine Sportsmen's Show in Augusta (usually right around April 1) and the Eastern Maine Sportsmen's Show in Brewer.
http://www.mainesportsmanshow.com/
http://www.conservationassociation.org/sportsmensshow/sportsmensshow.htm
I think a duck tub presentation/demo would go over well! You also might find some clients interested in coming up to try a new way to chase sea ducks.