SNES Classic Edition pre-orders shall be available at six retailers, pre-orders starting at different times

According to Nintendo's official SNES Classic Edition website, the system will be available via six different online outlets. These outlets are Amazon, Best Buy, GameStop, Target, Toys R Us, and Walmart. Different websites will be accepting pre-orders at different times, but unfortunately, the times at which these pre-orders start are currently unknown. Some outlets, such as Best Buy and Amazon, have already taken pre-orders. It is advised that customers select a specific outlet and bookmark the webpage and/or keep a tab of the page available throughout the day in order to check for when pre-orders become available.

from GoNintendo