Where to find composite material used on seat bottoms?

[DirtNasty]

have an 02 22i and have a seat bottom that has been replaced with wood but I was wondering where I could find the grey composite material used on the other seats in the boat. Or what is it called.

[WakerideN]

marine starboard or you can go brand name king starboard
https://www.google.com/#q=marine+starboard&spell=1

[Ruger761]

X2 good stuff and easy to work with