Look in the yellow pages for a Plastics store. They sell all sorts of plastics from flexible stuff (used up here for sled runners) to solid plastics that can be drilled for recessed screws.
Bill
Nodwell RN110 out moose hunting. 4-53 Detroit, Clark 5 spd, 40" wide tracks, 10:00x20 tires, 16,000# capacity, 22,000# weight. You know the mud is getting deep when it's coming in the doors.