Your search for "20mm" revealed the following:
Off White w/ Navy Blue Ridges x 20mm - TGB4119
£1.00
These off white polyester buttons stripes of blue ridges as well as two holes for attaching to your project. Diameter: 20 mm Material: Polyester
Wood w/ metallic Silver x 20mm - TGB3938
£1.45
These natural wood buttons have a silver dot pattern and silver rim with four holes for attaching to your project. Diameter: 20mm Material: Wood
Deep Blue Abalone Shell Sprayed with Flashes of Green Mauve & Purple 20mm - TGB5674
£0.38
Diameter: 20mm