You can pick up a Thermos-brand thermos at Target (downtown). Or if "city target" sucks in that department, there's one at Roosevelt (take red line south to...Roosevelt, walk west for 1-2 blocks). I got a 1.5 L one when I was sick and needed to travel, so I could have hot tea between meal stops. Kept heat like a charm. Stanley brand probably works just fine too. Just honestly don't cheap out, you need a VACUUM insulated bottle. :)
Also if your office has a coffee maker (you have to have a coffee maker, right!?) it may have a hot water spigot/function. This can make ramen, oatmeal, or Lipton powdered cup-a-soup in a pinch, or a hot beverage of choice to go with a sandwich. Obviously not ideal but good for "backup food."