Source for bucket/thumb linkage spacers?

I’m looking to source some spacers for my pro-link thumb that I’ll be installing in the spring. I can get a local machine shop to make them, but that seems a little overkill and costly. Do you guys know of any online sources for flat steel spacers? Between 1/8” and 1/2” thick? ID: 2 5/8” OD: 4 3/8”