First off you most likely don't want a Glock Factory Threaded barrel, they are usually in 13.5 x 1 and are left hand thread. If you are looking for the ability to put a Comp on you should be looking at most aftermarket barrels in 1/2" x 28, that will take any of the Agency 417 Comps or the like.
Check out Agency Arms site, they have a dealer in Canada, they just aren't a member here.