both fromageries at march atwater carry some. I think the variety at fromagerie atwater (downstairs inm their basement) is better in terms of the higher end stuff. ..the saussage place upstairs also carries serrano and so do a couple of other places. My favorite 'cheap' serrano would be from Hamel on butcher row. But do a visual inspection to make sure they don't cut you a dry piece as their fridge sometimes dries it up. the more experienced salespeople won't do that but if a teenager is serving they don't always look.
Last year (or was it 2 years ago? times flies) there was a shipment of Bellota that came into town, places like "La Vieille Europe" and la fromagerie Hamel got a few hams but it was very expensive, after spending too much money on some, I stopped looking for it.
You could call them and see if they still offer it.
You can find "industrial" serrano ham pretty much everywhere, but it is a very pale imitation and not worth it.
Me think they do not have it anymore, because it was too expensive for the Montreal market (and that they did not cut it properly IMO)