Motine via Amazon offers Prime members its Motine 6-Piece Packing Cube Set in Blue for $11.99 with free shipping. That's $28 off list and the lowest price we could find. It includes grid storage bags and laundry bags.
For those in no rush, Happystore2016 via eBay offer this similar 6-piece set for $3.99 plus $3.99 for shipping. Note that it ships from China and may take up to four weeks to arrive.