M18 Heavy Duty Flat Washers (DIN 7349) - 18-8 / 304 Stainless Steel: Accu.co.uk: Washers & Spacers
Amazon.com: Zkenshan-washers M3 X 6mm X 0.5mm M3x6x0.5 New White Black Nylon Flat Washer Plastic Insulation Plain Ring Gasket, 100Pcs, Good wear Resistance (Inner Diameter : White) : Industrial & Scientific