i agree with the PP...Thirty-One is having an outlet sale next week, and there are some really cute lunch tote patterns. i'm not sure when the sale will start, because there have been some issues with the servers of the third-party vendor that is hosting the sale, but we've been told maybe monday.
I saw some at either Walmart or Target last week in the sporting goods section. Similar to the PP's photo. Varying sizes for small child (also would fit into tote bag) to one that would hold a good size lunch (for long day), plus two or three bottles of water.
They also carry the standard styles that have been around 10+ years.