I have had orders from Keepsake Quilting, Connecting Threads, and Thousands of Bolts (and others). Connecting Threads has the shipping to Canada down to a fine art - have never been surprised by additional brokerage fees from their shipments. I believe Keepsake Quilting shipments ended up with brokerage fees on top of the shipping charges, and I honestly cannot recall how the Thousands of Bolts worked out (sorry!).
I have had the most success with shipments via USPS.