Here at Caleb Components we offer two options of Shim Washer Kits (Shims to DIN 988 standard).
Our smaller sizes kit ranges from 8 x 14 x 0.1mm to 14 x 20 x 1mm
Link to purchase this product: https://springfasteners.co.uk/product/din-988-shim-washer-small-sizes-qty-1-box/
Our medium sizes kit ranges from 15 x 22 x 0.5mm to 20 x 28 x 0.5mm
Link to purchase this product: https://springfasteners.co.uk/product/din-988-shim-washer-medium-sizes-qty-1-box/