Good to know we can still get these parts, thanks. Let us know how they work!

Huh. Have a sheet of this stuff lying around. Gotta see if I can apply it to my HHR’s. Don’t even know the best way to cut it.

Assuming it's plastic or really thin metal, you want it slightly bigger so it's a friction fit. I did this with a plastic sheet of honeycomb once and I used a small scissors to cut one wall at a time just outside a circle I taped to the sheet. Unless you've got a laser or water jet, that's likely as good as you can do.

It’s aluminum, side-of-a-beercan thin. Cell are bigger than 1/4” but I didn’t measure.