Leaning post storage compartment

[CAP1]

I would like to add some storage to my leaning post and need a poly-plastic box or hatch type liner for it. I will add a hinge so the seat tilts up, but haven't been able to find some type of ploy storage box that will work.
I know I can make one out of starboard, but I'd like to find something in thinner poly already formed I can buy.
Needs to be approx 30" long, 8" deep, and 10-12" deep. I'll have the exact measurements shortly.
Any ideas?
TIA.

CAP

[CAP1]

Anybody?

Guess I'll be buying some starboard and making my own.

[ccat]

I made one to go under my leaning post out of starboard works really well

[DJD775]

Check out SSI plastics.
http://ssicustomplastics.com/bins.htm