I'm starting a scratch built bucket but I can't find the materials that I need. I've decided to use plastic instead of cardboard or poster board. The plastic that I'm looking for is the kind used for "For Sale" signs or business signs, sign boards is what I think they are called. My problem is that I can't find a board big enough that will accommodate the size of the inner and outer bucket. Can anyone tell me where I could find these boards? Does anyone have any suggestions?