Don't know if W.W. Grainger sells in Canada or not but they're another source for industrial #41 chain.
As for your chain jumping off, make sure your alignment is good. The tensioner, if you're using one, must be aligned with your engine sprocket and the one on your rear wheel. Misalignment and too much, or too little tension can cause your chain problem. Also check that there is no binding in any of the links that keep the chain from tracking over the sprockets smoothly. I've seen a couple of those Chinese 415 chains that had a twist in them and rollers that didn't roll. Industrial grade #41 chain is the best way to go. It runs true and it won't stretch as readily as the kit chain. Good luck.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"