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Personally this is what I would do.
If it is the Sumo's you want and you can find them in the USA, drive across the boarder and buy them. If the USA does not have them then locate some in another country, then contact the rep for that country and ask if they would ship them to Canada.
Years ago I wanted a set of Pirrelli P6000 for my X the only place I could find them was in Turkey and the UK. I contacted the UK rep and he helped me get the tires to Canada 10 tires in all. Yes I still have 8 new tires stored in oil drums in my basement. The 10 tires came over in a shipping container with out extra charges, however it took 5 months from the time I ordered them to the time I had them mounted on my car.
TonyK.
Grimsby Ontario Canada.