Have you heard of swivel pads? Seriously I had thought it got something to do with iPads. Really. Never once would I associate it with bolts. Right.
Anyway, if you check out the link above, you’ll find all sorts of swivel/toggle pads with different sizes and types and made of various metals.
This is what I got off the website, “Reid Supply Company has thousands of products for your tooling component needs. You can find a variety of toggle swivel pads for your bolts in either a serrated or flat bottom in your choice of sizes and material. Reid is the only place to shop for your tooling replacement parts.”