Went to the dealer. A different salesperson this time, he pulled one off the shelf.
It's basically a 9 x 11 x 1-5/8" box, sealed on the left and right, open on the top and bottom. Sits vertical (11")
I told him I could make one, he just said to use stainless 4" through the wall. Attach it to the box.
Thanks for your replies.