Amazon Essentials 4-Piece Slim Packing Cubes, Travel Accessories Set, Luggage Organizer, Suitcase Organizer with Double Zipper, Mesh Top, Space-Saving, Gray (Previously Amazon Basics)

You probably won’t find something those literal exact dimensions, but fabric is flexible. Something within half an inch to an inch either way will probably fit well enough depending on how you stuff it. If it’s a little too small you can stuff other loose items in the dead space. https://eaglecreek.com/products/pack-it-reveal-slim-cube-m? https://www.amazon.com/dp/B014VBI9YC? https://www.backcountry.com/patagonia-black-hole-6l-cube