Thermos makes a pretty good stainless steel thermos.
If there is a UN base near you they should have them, but you should be able to find something suitable in the local kitchen supply stores.

Hey, did you know trying to clean stainless steel thermoses out with bleach kills them, I was so surprised to find that out.

and what is the plural for thermos?
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May set off to explore without any sense of direction or how to return.