Plastic covering on exterior bulkhead

[Drumhead]

Hello,
I removed the rear bulkhead from my '87 Mainship DC40
To replace. Does anyone know where to buy the outer plastic skin on the exterior of the bulkhead? It appears to be approximately 80mil and has an off white/tan color to it. Any direction would be great, Thank you

 

[Comodave]

Do you have a photo of what was there?

 

[Drumhead]

I will post a picture today sometime. Thank you for your response.