I know this is an old thread but here we go...
M's were available in Canada. I have seen a couple of them. The first one I saw was circa 2004 and I had never seen one before. They are much less common than other Boys. I eventually acquired one from a seller in Hamilton Ontario. It was the first generation model with the metal wheels and I continue to use it as my regular mower. It's given me some grief over the years but given its age and amount of use I'm reasonably happy with it.
The mower had a sticker affixed to it indicating it was sold by a LB dealer in Hamilton Ontario Canada. These were very expensive mowers when new (at least $1000) and that's why I believe they are few and far between up here.
Yesterday, I saw a M for sale for $70 on a local buy and sell Facebook page. It was located about 40 miles away in Petrolia, Ontario. Seller told me he sold it. So they around you just have to be patient. There is a guy in Toronto that has an add on Kijiji selling a M with the newer style wheels. He wants $450 and says its in very good shape. https://www.kijiji.ca/v-lawnmower-l...l-3-speed-self-propelled-lawnmower/1289741873
As for the Duraforce models they too were sold in Canada. I remember looking at a 10525 at it was about $750 to $800 at LB dealers in the early 2000's. I did not have that kind of money for a mower. A few years later I purchased a 10527 and 10527 both used but in good shape.