I've been eating a lot of canned soup.

How long is your route? If you have a refrigerator at work, I wouldn't think a 20 minute transit would do anything to most lunches. I'm contemplating making those family sized (I eat a lot) rice a roni packs the night before, and refrigerating them in tupperware, bringing them in, and microwaving them at work.

Unless you have a really long commute, I doubt a cooler is necessary, unless you don't have a refrigerator at work.