https://www.leevalley.com/en-ca/shop/hardware/fasteners/washers/116357-lee-valley-brass-countersunk-washers
Lee Valley Brass Countersunk Washers - Lee Valley Tools
lee valleycountersunk washersbrasstools
https://caterpillar-red.com/50-x-nylon-countersunk-plastic-machine-screws-m4-x-30mm-plastic-bolts-nuts-washers/
50x Nylon Countersunk M4 x 30mm Bolts, Nuts & Washers
Natural nylon M4 x 30mm countersunk bolts include 50 nuts and 50 washers, with a crosshead drive and flush head for neat insulated fixing.
nyloncountersunkxboltsnuts