Larry Fine posted this a few days ago, unsure if they'll ship to Canada though. $170 hitch:
Cheaper from their website! $119!!! But doesn't offer shipping outside USA:
Motorcycle Trailer Hitch for Honda ST1300 with 1 7/8" Ball | eBay
A Motorcycle Trailer Hitch for Honda ST1300. This striking motorcycle trailer hitch is designed to fit all model years of Honda ST1300. -Fitsall Honda ST1300 model years. TRUMAN Hitch. With theTruman Hitch on your bike, you can haul almost anything almost anywhere.
www.ebay.com
Cheaper from their website! $119!!! But doesn't offer shipping outside USA:
Honda ST1300 Motorcycle Trailer Hitch 2002–2013
Get a quality trailer hitch for your Honda ST1300 from The USA Trailer Store. Our trailer hitches are strong, durable and designed for a reliable connection. Shop now and enjoy
theusatrailerstore.com