I got mine from Dante's. Year One sells them, probably at a higher price, and other places also. I've seen some made from black tag board, but in that case, having an original as a template would be helpful.
Pretty sure that's where I bought mine too--well worth the cost. Quieted down the interior noise a good bit. Put in a new package tray and it's like a whole different car...then you start hearing everything else that makes noise.