Because I have access to a hot plate at work I use a Chinese style lunch box. Similar to the Indian Tiffin but the Chinese style is meant to be heated.
http://www.amazon.com/Tier-Chinese-Lunchbox-Sold-Shop/dp/B00012F3SQ/ref=sr_1_4?s=kitchen&ie=UTF8&qid=1444530454&sr=1-4&keywords=chinese+lunch+box