When i was up in Ontario (about 4 years ago now) you could buy the 200 count bottles of AC&C at walmart for about $8 i think. They are much more expensive at shoppers drug mart as they are about $10 for 100 AC&C's. AC&C's are your best bet as they are the cheapest form of OTC codeine in Canada. They have 325mg's of Aspirin, 15mg's of Caffeine and 8mg's of codeine. Other products such as Mersyndol which has 325mg's of Acetaminophen, 5mg's of doxylamine and 8mg's of codeine are available but they cost a fortune (about $20+ for a bottle of 100) and you can't take anymore then say 5 as doxylamine is water soluble and as it's a anti-cholinergic will make you delirious in high doses which is no fun.
I was never carded in Ontario but then again i was 28 at the time. Still i sometimes to this day get carded for smokes and booze so i guess all the healthy living is responsible for my young looks

. They can card you though all the same if the pharmacist wants to.