Replying to Making Tramp Skis

im making duct tape shoes for them. but i need something for the skis themself. i know i cant use wood because if i lad wierd doing a spin ill ruin myself, it will also be awful for my tramp. so. im thinking long, medium density blocks roughly 50"x3"x1" and wrap that in duct tape as a rienforcement, i may also put used d-size batteries on the tip and tail.

anyway, im mostly wondering where i could buy the foam, or if anyone knows of a good substitute i could use.

thanks.