I believe that I've seen the Shockwave 18.5" sold in Canada, but maybe I was looking at the so-called JIC models. Anyway, Mossberg does manufacture an 18.5" Shockwave:
https://www.mossberg.com/product/590-shockwave-7-shot-50639/
To be more serious, I would indeed like to buy my wife a Shockwave with 14" barrel and install one of those rubber inserts in the loading port that allows Federal shorty shells to be fired and reliably fed, but I don't want it to be suddenly be re-classified as either banned or restricted next week. I've already got one useless firearm and I don't want to start a collection. I have an RPAL, but I do not want to deal with the hassle of owning a formerly NR, now instantly-R firearm, either. The rub is that our safe only allows a maximum length of around 30", possibly 31" with that curved raptor grip, but I'd have to actually try to fit it in there to know for sure before buying. Even though I know I do not have to, I have always stored NR firearms in our neutron-star-heavy safe and I want to continue to do that. Maybe as time goes on we'll come to know with more or less certainty what the final classification will be for that amazing 14" Shockwave, which seem more to me like a really big, incredibly powerful handgun than a long gun. I believe that I could grow to love that shotgun as much as Iloverevolvers (which I won't own because they are Restricted).
Edit: The 18.5" version is indeed sold in Canada at one of the CGN forum advertisers:
https://www.firearmsoutletcanada.com/mossberg-590-shockwave-12ga-3-18-5-barrel.html
Notice the overall length of 31", which is pretty tempting.