Square Backdraft Damper

I am trying to locate a spring loaded Square backdraft damper (non motorized) to prevent heat from rising up from my stove into my cold air returns when the stove is idle. I can see tons of round dampers but no squares. I need a square 11"x19" or 8"X10"

Anyone know where I can get one?

Thanks!

Square ones are probably a lot more expensive, maybe make up a piece of sheet metal with a piano hinge and light spring? Might be a lot cheaper.

http://www.emwhouston.com/backdraft-dampers.htm

http://www.drillspot.com/products/51039/Dayton_4H ... aft_Damper

http://www.snaprite.com/

http://www.mcmaster.com/
(see pg 646)

thanks

Thanks, those are not bad at all. I must have been searching on the wrong terms....