this looks like a modified brake disc from a truggy/buggy. Racers Edge among others make these. They are good because they resist fuel unlike the cardboard shoes on some of the 1/8 scale buggies.

Id love to know which one he is using as they come un a bunch of different sizes? then all youd have to do is match up the mounting holes.

Better yet I would pay Himalaya if he would make 4 and send them to me!!!