Nemor, if you have extended medical through your employer then you shouldn't need excess insurance beyond that, as it is very good coverage over and above the standard MSP plan.
If you don't have extended medical then you will need insurance, but don't buy it from expedia.ca. Try BCAA for a trip package. You need not be a member, but will be offered a 5% discount for booking on line. Their rates aren't bad, with coverage that is almost as good as most employers' extended packages (eg with Pacific Blue Cross).
A number of Canadian credit cards have travel insurance packages as perks for the (sometimes hefty) annual fee. Unless you have a bare bones credit card with no extras, see what's offered with that card as well. Usually one needs to book and pay for the trip with that card for coverage to be offered, so read the details at the card provider's website.
Again, though, if you've got extended coverage you should be in fairly good shape.