I have never seen a Canadian advert for pinfire cartridges, but it is not difficult to imagine gun dealers in Montreal and Toronto importing primed cases. Most complete cased gun examples I’ve encountered included loading tools of some sort, so loading one’s own must have been commonplace. With the pinfire system remaining popular in France, there would be regular trade with Lower Canada, so probably a ready supply. Unlike in the US in New York and Baltimore, there does not seem to have been any local gunmakers making pinfire guns in Canada.
There is an auction coming up here that includes a great many early Canadian-made percussion guns, no pinfires:https://live.millerandmillerauctions.com/