I buy Martelli or Clover blades from Connecting Threads when they're on sale. It makes the blades more affordable, and saves me the cost of sharpeners that don't really work. I have never found anyone with a home sharpener that gets blades good enough to be worth the effort, IMO.
EBay can be a good source, too, as long as the shipping to Canada isn't too crazy. I've never purchased from eBay because of the shipping charges.