I've made some of those dogbones before, using [roof] flashing and scissors/tinsnips, then some filing to make them prettier. Tedious, but they worked OK.
The rubber is harder: they are a molded part. I made something like them with flat rubber sheet, they tended to drag slightly but worked OK with some silicone grease added and some just plain working-them-in for 100+ moves. They are a dust cover to prevent the slow ingress of grit into the little pivots.