Yeah - those offers are never available in Canada. Actually, I haven't looked into that for years....
We need to get more people to join this swap!
I'm actually in Canada too, and there are a couple of decent services here. I've been looking into them because I'm moving to Nunavut and I doubt I'll be able to walk to a comic store there, so I found http://www.comicpull.com/
, also, I was surprised by the amount of stores that will ship your comics to you. Dark Horse Comics in North Bay will hold your books and send them to you in a monthly pack at a reasonable price, I bet you whatever the closest store to you is would do that too.