Recently I purchased and installed a NU-Tone Whole house fan in my attic. I had to make a 36"x 30 3/4" cut in my hallway ceiling and mount the fan to the bottom of the rafter in the attic. It is now approaching the fall/winter season in Michigan and I need to find an "interior insulated cover" to install over the louvers of the fan. Can you please recommend or find someone that sells these? I've seen one before that was plastic and had a piece of insulation in it. It then mounted by magnets and screws. That is what I am searching for now. Thank you..