There is no problem getting a factory Rem 870 up here. They are pretty cheap. The Norinco HP9 is a very good copy, and holds up well. The same can not be said of their Ithica clone.
The Norinco's sell well because they are at least as good as the Express 870. Also, since the 14 inch guns are legal here, it's easier to import the Norinco's. Your State Department don't approve export applications for NFA items to civilians, even if it's legal in the importing country.
Where I paid $400 including all taxes for the Norinco, a Rem 870 with a factory 14 inch barrel runs about $1200.
The home defence 18.5 inch 870 with the factory mag extention sells for $379 plus taxes. The comparable Norinco sells for $299.
One other reason the Norinco's sell as well as they do is the factory rep from Remington made a rather unfortunate and poorly thought out statement about Canada, and the company has been shit on heavily by our shooting community ever since.