I would contact Don Nieser at Commodore Aerospace.
Commodore Aerospace Corp.
6221 Commodore Lane OKC, OK 73162-6814
Phone: 405.722.4079 Cell: 405.503.4686
nieser.02.337parts@juno.com
You could check with Owen Bell at Aviation Enterprises, he has molds for some items and can make new ones.
Owen Bell
615.865.1802
owen.bell@juno.com
The part you want is #17 on the illustration. This is from CessnaParts.com (ouch)!!!
1513049-1 SCOOP
(List Price: $ 310.41) Call for Availability $ 248.33 (EA)
You should buy the seal also #15. This gets torn up from working in the radio bay. Don't just rely on the tray for the moisture, you should try to keep the moisture from intruding from the start and the tray is there for insurance.