The dealer I've always used, and can recommend highly, is Manchester Honda.
http://www.manhonda.com/ If you call them, be sure to ask for the "catalog department", not parts. You will pay full price at the parts counter.
That being said, they wanted $178USD for the sensor for my '86 Si. I got a universal at a generic parts store for $20USD.
Dunno if any of this helps since you're in Canada. -scott