I've not come across plant specific Canadian dealers, only fish. But some stores will do mail service, and there is one in Vancouver that ships plants (and fish), here's the website. Vancouver Aquariums, tropical fish and plants for sale
I know April personally, she's very reliable and her stock is good. Plants like fish vary from season to season of course, you can email her to see what's in at present, though if it is very cold where you are you might be better waiting for warmer weather.