Materials for a sousaphone shoulder pad?

[matrota]

Hello, I am doing a science fair project this year in which I am creating an attachable feature to the sousaphone that will attempt to distribute weight evenly across both shoulders. I am going to have a pad on the right shoulder with a strap attached to the pad, going around the bottom tubing of the horn, and hooking back onto the pad. It is adjustable in length, and i have the design figured out, but i need information on what kind of materials go into a pad, and any information would be greatly appreciated. Thanks!