Many stores only ordered 1/3 copies when the game was released, and sometimes only if someone pre-ordered from said store. Sins has not been hyped to the high heavens so these stores are taking their dear sweet time stocking the shelves with Sins.
I had asked a local EB games in NL when they would have Sins stocked and was told it would be the 8th. There was a post a week ago about someone in Halifax getting on of the only 2 copies in either the city or the province.
Call around, department and computer stores are your best bet. If do not want to order online but are getting desperate, many grocery stores have electronic departments that have a very slim chance of having it.