Greetings! Although I am new to the sport of airsoft, I am not new to the sport of finding good shops for tactical gear, and would like to make a couple of suggestions. They aren't in Kingston but they are fairly close. The first is One Shot Tactical in Trenton. They have some awesome milspec gear there and the prices are fairly decent. No airsoft guns, but that is to be expected as they usually cater to competitive shooters and law enforcement types. http://www.oneshottactical.com/
The second is Hero Army Surplus in Oshawa. Hero's is more on the paintball side of things but still worth checking out. The only really big problem with Hero's is that I get in there and don't want to leave... like ever. http://www.heroarmysurplus.com
I hope these places are helpful for you if they haven't been posted already.