I've had dreadful experiences trying to find BBs and Gas (or any useful equipment of any kind, for that matter) in stores like Canadian Tire outside the city. You'll probably be okay trying various stores in the city, like you mentioned, but you might do well to check online as well.
If Canadian Tire has any of these things listed on their website, you might be able to track the right thing down without having to waltz all over the city. That is, of course, if you don't have any luck with your local store.
But I can say this for certain: don't try getting anything useful out of a CT north of Newmarket. They never have anything.