The apartment I bought has 2 old units for heating and AC (McQuay and Xpediair), but they're both missing the top covers. At first, I thought about trying a plastic mesh used for covering gutters, but that wouldn't look good. The distance from the shelves the covers would rest on to the top surface of the units is 1 inch, so something about that thick would be good. Can you recommend something suitable? Someone told me there might be honeycomb panels but I don't know where to find them. Thanks.