One method: Deal with them directly and manually confirm shipping (sellercentral.amazon.ca/orders-v3) Canada Post has a free Solutions for Small Business membership with some shipping benefits.

Second method: Find a logistics company that will sell you shipping labels and update AZ sales automatically for you (or you can still do it manually).

What you will not able to do is buy shipping through amazon.ca directly -- that is currently reserved for shippers from China.

-;-