Go to your local West Marine, daylight orange smoke flares, Coast Guard approved, if you want the 25mm offshore kind, spend the bucks, but why? These don't go bang but do put out a mess of smoke.
http://www.orionsignals.com/Marine/P.../handheld.html
4min can on the bottom of the page
http://www.orionsignals.com/Marine/Products/solas.html