I feel so stupid for wasting so many months trying to get a new heater plenum from QuiteRide only to inspect my original plenum that I now think is repairable.
It has been on a shelf for some time and the back side of it had completely separated and is in a couple of pieces. I put the whole thing off the shelf and find that the front of it is much more durable than the back. It's dirty, faded, and maybe a little moldy but usable. All I have to do is rebuild the backside and figure out the channel inside. I could have had this done a year ago.