I also saw the Notebook Kit being sold at EpiCentre at Ion Orchard for S$39 (after 10% member’s discount is S$35.10) which is slightly more expensive than Design Museum Shop. Challenger at IMM on the other hand is selling for S$29 (after 10% member’s discount is S$26.10) which is the cheapest among the three shops.
I saw the Cool Feet being sold at Challenger at IMM for S$18.90 (after 10% member’s discount is S$17.01). Head down there if you want to get the Cool Feet as a standalone product.