Assuming you are referring to the two rectangular blocks with 2 counterbored holes in each, then Nylon 66 would be my first choice for those. It has many other names such as Ertalon - try google.
We used it in the Aircraft industry for wear strips on various mech test projects, where we tried to break airframes by repeated loading/unloading. It has great wear, chemical and impact resistance and a melting point in excess of 250 deg C.
There are lots of places on fleabay selling off cuts in various thicknesses, most with 'free delivery'
Ian