For that type stuff, I've cut my own barrel shims with scissors from stainless sheet shim stock purchased from McMaster-Carr. I've used a drum sander on Dremel to smooth out the curve but probably not really necessary. I currently have a few sheets of stainless (Rc40-45) in .003 and .005 thickness. If you think you can use it, I'll mail you some. Yours for the asking. They were very low cost items.