You've got a bunch of options in the Toronto area, Ontario Beer Kegs, Canadian Homebrew Supplies, Beer Grains, and probably others. I don't know how long of a drive that would be for you, but I usually just order online and have it shipped.
Toronto is about a 1.5hr drive, Oshawa is about a hr.
I have ordered from ontariobeerkegs before and have been pleased. I have never been to a true brew shop where I can buy malt in other forms then extract and was curious to see what it looked and smelled like. I bet my brews would be a little more interesting if I could see, smell, and taste the grain.
Ontariobeerkegs.com website seems to be down and I want to do a brew this weekend. If there site is not back up soon I wont have time to have it shipped