Tiny, totally, totally cramped hardware store on Centre street just by the metro.
The dude has everything in there. You don't think he does, cause it's small, but he does. X-mas lights in June? Check. a set of allen keys for your bike? Check. A housewarming gift on the fly? Check.
You can't actually browse or find anything yourself so you need to go to the counter and ask him and then he'll be like: "pas de problème" and he'll come back with your thing and then you'll be pleased that it'll be a heck of lot cheaper than what you'd pay at one of those large retail chains. So you win.