OP, since the sale starts at Zellers Friday, if you go in tonight and grab the last one, you can go in on Friday w/ the bill and get them to fix the price. Sometimes, if you go to one of the smaller check outs (like the electronics) w/ the flyer, they'll do it for you the day before. I think it depends on the clerk.
BUT, make sure that the *one* they have left is not the floor model, has it's tags attached, the manual, plastic and otherwise looks *new*. You could also call the (other) Zellers/TRU in your area and see if they have others and/or if TRU will match the price. I've never had luck w/ a TRU price match (on anything) but others have. Probably depends on the clerk, store and sale...
Otherwise, you'll have to wait for the 2012 stock (of this or others) to come in before buying a seat to get what you want, so make sure you check the timing of when LO will outgrow the current seat! Such a pain!
tam