Most of the providers offer a "prepaid" plan, which would be what you're looking for. Unfortunately, as you're well aware, prices in Canada are generally higher than what you'd see in Europe. But, in theory, you should be able to walk up to a (insert provider here) kiosk in a mall and get a prepaid sim and load it up with 30 days worth of whatever you need.
I stumbled across this comparison site, but I can't speak of its accuracy:
http://www.cellphones.ca/cell-plans/
Obviously you'll have to dig a little deeper about extra costs (sim, long distance, etc.) as well as coverage, but it is a starting point.