You can get HDPE (high density polyethylene) online or if there's anyone local who works with plastics in 3/8" sheets in a variety of colors including basic black, sometimes as scrap. Essentially the same stuff one uses as a cuttinhg board in a kitchen. It cuts well and will shape with a file, rasp or sandpaper. I leave it full width where it mounts into the skegbox, then shape a narrower blade. Cheap. Drawback: considerably heavier than wood.