Check out Numrich, they often have used barrels barrels over 105mm, that will fit your revolver. You will need to go through a broker to get it into Canada easily, unless you want to go through months of acquiring paperwork.
There are other options as well. A barrel can be profiled and threaded to fit your revolver by just about any gunsmith with a lathe. Depending on how fussy you are about the profile, will determine price.
There is also a Smith and Wesson repair center in Canada, that can supply/fit a new barrel for you. I don't remember the name of the place. Murray Carlton out of Victoria used to be the S&W repair center but he retired last year and another company picked it up.
Bits of Pieces, out of Delta, BC can either make up barrels or bring barrels in for you. Won't be cheap.