For cross-border mail-order, try B&H or Adorama in New York or Freestyle in California. I don't know much about Canadian film prices or shipping charges from any of these places to Canada, but for in-US shopping, prices from any of these generally beat local film prices, even considering shipping -- at least, assuming you want to order more than a couple of rolls. Freestyle's prices are generally best for its house brand (Arista), which is made by various companies (Ferrania for color, Foma for B&W with older stock by others). B&H and Adorama are generally better for name-brand film (Kodak, Fuji, Ilford), particularly if you're willing to buy grey-market film.