Roland KF-20 and KF-25 do not have a dedicated dust cover available for purchase. Use a commercially available piano dust cover sized to fit the instrument. For dimensions, refer to the product page.
KIYOLA KF-20: https://www.roland.com/global/products/kiyola_kf-20/specifications/
KIYOLA KF-25: https://www.roland.com/global/products/kiyola_kf-25/specifications/