Walmart offers the Rubbermaid Lunch Blox Sandwich Set for $7.92. Opt for in-store pickup to avoid the $5.99 shipping fee. (Target charges the same.) That's the lowest price we could find by $6. Designed to save spaces in lunch bags, these reusable containers are BPA free and dishwasher-, microwave-, and freezer-safe.
For in-store pickup only, Walmart offers the Rubbermaid Mini Ice Pack for $1. That's tied with our February mention and the lowest price we could find by $3. It's reusable and fits inside or snaps to the bottom of your container.