[maple_leaf_eh]

There is a plastics supply business in downtown Otter-wa (south side of the street, first block east of Bank, one or two blocks south of the backdoors of Esplanade Laurier). I bought some pieces of KYDEX there to play at to make rifle cheekrests.

My second and more pricey suggestion is Lee Valley Tools. You might not find big pieces there.

How about one of the machine tool retailers, like Busy Bee? Or do they only sell tools, not materials?