>>5253515>>5255176Try Hobby Base #PPC-Tn11 Ultimate Joint series - PC Ball Shape Joint Set [G Gray].
I got two joint sets off ebay. They're 13 bucks each.
I don't know if they can be found cheaper somewhere else.
I was fearful of breaking, losing or just normal wear and tear of my robotrap's joints. After careful examination of japanese twitter pictures I came upon these.