check valves

[farmerjo90]

Does anybody know where I can get a check valve in Canada. It appears as though there are holes for powerheads drilled into the overflow wall of this tank. This means the tank will siphon out onto the floor during a power outage. I know that marine depot in the US sells these valves but would rather find something locally and rather quickly. There is a ball valve of course but then you have to be home to turn it off (as if that is going to happen).

cheers
shirley