With orders of $25 or more, Amazon offers Prime members the Wildkin Munch n' Lunch Bag in Peace Signs for $5.62 with free shipping. (Non-members can spend $35 to qualify for free shipping.) That's $2 under what you'd pay in-store locally for any Wildkin lunch bag, although most merchants charge $13 or more. It measures 10" x 8.5" x 5" and folds flat for storage.

Note that this item is part of Amazon's "add-on program" and can only be purchased with an order of $25 or more.

Update: The price has increased to $6.92.