Try buying some thin brass shimstock and cutting/drilling washers from it. I bought a big sheet of .015" brass and have made several sets of washers, works great and is nearly invisible.
To make em, I just draw/trace the outside diameter, mark the center, drill the center and cut to shape with sturdy shears.
They are not perfectly round, but that is hidden by the scales. If you are really anal retentive, you can just drag it edge first across sandpaper till it is round enough for ya.
By the way, they sell that shimstock at Ace hardware, Lowes, and many craft stores. They even sell silver as well!