Plastic Bunk Boards?

[Kurt]

Does anyone know where I can buy planks of the plastic bunk boards that are commonly found on Boatfloater lifts. I am needing approximately two pieces that are 16 feet long. I am wanting to constuct a walkway on each side of my lift so I can easily wash the hull. An example of the material is the black plastic bunks shown here.
http://boatfloater.com/gallery/gallery_main.html

Thanks, K