After much on-line research I purchased the Barrecrafters US-1400 Multi-Use Bar Rack and US-217 Deluxe Canoe Carrier. The rack and carrier are solid and secure. The rack comes with key locks to prevent theft. The canoe carrier consists of gunwale supports which attach to the bar rack, and includes a ratchet system with non-stretch straps.
I also purchased the "Maine Roll On" from Maine Outdoor Products, which is a big help in putting my canoe on and off the rack without the need for assistance. I have also posted a review of that product.