If you have something to ship from the US but they don't ship to Canada - Freeport Forwarding is a great service to use.
You need to open an account with them first (free of charge). In return they will assign you a "box" number - use this as you would a suite number!
Once the account is open you can have your items mailed to them and they will hold it for you until you are ready to pickup.
There is a fee of $3 USD/parcel held and $20USD for a set of four tires.
The front office can be a bit messy at times, but no worries. The staff are always able to find your parcel.