Plural for thermos is: Thermoses
You really can't go wrong with Thermos / Nissan / Stanley brands.
Pre-heat the thermos with boiling water for 5 minutes before putting your hot liquids in,
Also instead of putting on the small plastic cup which comes with the thermos, leave it off and stash it in your kit bag. Take a small (depending on Thermos lid size) piece of polar fleece or equivalent and cut to size so that it fits snugly into the lid of the thermos. Now put the lid on the thermos. If you have a small and thin enough thermos, next take an old (or new) spare wool sock and drop the thermos into the sock.
With the polar fleece in the lid and the wool sock covering the thermos will keep the hot beverages hot for 16-20 hours....and longer if the thermos is rolled into a sweater, pair of pants etc in your kit bag. Often in the warmer months, the coffee or tea is still hot enough to drink the next morning.
A thermos, this size (24 oz) is perfect for this.