Got a friend in the US?? Give him the money to purchase them (in USD!)with delivery to his place. Go visit for a weekend and take them to a tire store and have the wheels mounted and then drive home. What are the chances that Canadian Customs might remember your car going into the US with the wheels that were on it??
Customs fees and taxes would probably eat up a big chunk of money, not to mention the shipping but I don't think the shipping charges are going to be be that high. It's still based on weight, package size, and the distance.