Not sure about a thermos but I absolutely love my contigo water bottle. It's super light and keeps all my drinks cold for 12 hours. https://www.amazon.com/gp/aw/d/B00IR77FAG/ref=mp_s_a_1_sc_2?ie=UTF8&qid=1481449000&sr=8-2-spell&pi=AC_SX236_SY340_QL65&keywords=contigo+ahefield