In Toronto, you are not far from most of the large U.S. RV manufacturers, who are nearly all clustered within 30 miles around Elkhart, Indiana. Almost to a company, they have an option to build a trailer to CSA standards. But, since you have to drive to the U.S. to pick it up anyway, why not also get one with the lowest possible transportation charge added to the price (which every dealer does and which is always based on distance from the factory)?
So, if CSA is important to you, just special-order a 5th wheel from a low-cost dealer as close as possible to Elkhart. As just one on-line example that I know of--RV Wholesalers is just over the Indiana line in Ohio. And I am sure some forum members know of many others.