Depending on the length of your commute, ambient temps and whether you like salads (long list of ifs) try salad jars. My wife and I use them. I believe they are from Pampered Chef. Heavy gauge plastic with a lid split to contain dressing as well as secure the salad. Holds a good sized salad.
I know, you didn't imply salads, but thought I'd toss it in as an option.