I'd say HMV and Amazon are your best bets. EB games has been thinning their PS2 collection pretty heavily in the past 12 months. HMV stocks a full shelf of PS2 games and I have found, on numerous occasions, Persona 3 FES and Persona 4 new for $30 each.
Atlus routinely will reprint their games, especially their PS2 titles. Usually Amazon will pick up on these copies, which is where I picked up Digital Devil Saga 1 & 2.
I don't know what the locally owned video game store scene in Ottawa is like, but they will most likely have a copy, but it won't be cheap.
Then there always is eBay....
Also, for Persona 3, you could always pick up Persona 3 Portable, although I don't really recommend it for new players. I know the game was made to attract new players and be more friendly towards them, but I just don't see that much improvements in that regard. The game, to me, removes a lot of the necessary presentation in the storytelling. I really only recommend it to people who just cannot find the original or those who have played through the original and wouldn't mind the extra female story and/or a portable version of the game.