I'd recommend just looking on ebay or craigslist, as thats your best bet to get the biggest selection. You can also try
http://www.gamestop.com/default.asp?sect=1267
Stores in Toronto:
A & C Video Games - 416-923-3066
Game Kingdom - 416-913-2509
Game Shack - 416-351-7065
Game Zone - 416-934-0874
Jack's Video Games & Variety - 416-654-5500
Microplay Games - 416-363-8989
Sonic Boom Music - 416-532-0334
Video Games & Choices - 416-651-8765
Video Games Plus - 416-636-5774
Video Vibez - 416-656-3853
Xtreme Games Interactive - 416-534-8885