Does anyone know of a place where I can order a fan to put in my doorway? I'm talking about the square units that mount on an upper corner of the doorway. I need two in order to move some heat around my house. I just installed a pellet stove today. I'm fairly happy with how the heat moves, but I'd like to give it a little push. The local hardware store has the fans, but they are $30 each. That seemed really expensive to me.