I'm never an advocate for buying gaming materials purely for the sake of buying gaming materials. With that in mind -- what sort of supplements do you want? If you're running a grim and gritty spec-ops game, then you'd want very different supplemental materials than if you're running a Buffy-style cinematic FX based game.
As far as Canadian shops go, IIRC, Cyberdungeon.com is located in Canada. Amazon.ca also should have a nice selection of stuff.