IKEA's STUK hanging shoe organizer, great for holding singles : r/ketochow
VOLKSLAND 6 Shelves Hanging Organiser, Shoe Rack with Deep Pockets for 12 Pairs, Over Door Hanging Storage, Shoe Storage Hanger for Closet and Dorm Door : Amazon.co.uk: Home & Kitchen
SKUBB dark grey, Storage with 9 compartments - IKEA
Ikea Storage Solutions for Minimalists on a Budget - Remodelista