Try this:
http://www.boschusa.com/AutoParts/PartFinder/PartFinder.asp
and see if Canadian Tire (or any auto supply store) can get the one for your car.
Replacing both might be a good practice on a car with only two O2 sensors, but I haven't heard of anyone replacing the four that are on my cars and later models, when only one is acting up.
This from the home page FAQ gives a link to the 3 digit codes your car gives.
http://www.contour.org/FAQ/FAQ.php?s=probs&display=checkengine
