Summary

Made some adjustments on the original. Changes were that I shrank the circle to make it fit the metal discs/washer I had bought. These fit for 1.7 cm (17mm) holes in the middle (a bit loose, so might also work for 15-16mm, but not tested).
I glue the metal disc in place so it dont wiggle inside and also glue the top on to make it look a bit nicer.