I'd like to see a thermos

[The Wanderer]

Nothing major, but a thermos or an insulted mug might be nice. I don't think it would throw off game balance. 

[Mroz4k]

I agree. It would be great if we could have an item, which would be very heavy to carry, but could store some heated drink and would keep it "heated" for up to two hours. 
I also believe it would not be such a bad idea. I assume it would be extremely useful in those situations when outside temperatures are brutal but you have to keep going and can't stop for long, you would make a short stop with fire to regain some heat by cooking up tea and was able to take some extra tea with you. It would be a life saver to have it hot even two hours later when your temp would once again be pretty low and you would have already used up your "warm core" temp bonus.

For a long time, hunters, skiers, boarders, fishermen, mountaineers and hikers have all prepped a warm drink to carry in an insulated cup or a Thermo bottle with them. 

I think fair stats would be these ones:
Stainless steel thermos cup: - 0,65 kg empty, 0,9 kg full.
can carry 1 heated drink of 0,25 kg - all teas or coffee. The drink will stay heated for 2 hours.

In reality, thermo cups weight somewhere from 0,35 to 0,45 kg and can keep a drink heated up for up to 4-5 hours.
Thermo bottle would be heavier, obviously, but one could argue that such bottle can hold up to 1 litre of liquid in it and that holds entirely new problem of "mixing" drinks in it.

[Ape88]

I would want this but with a more real life length of time for keeping something warm.

[Mroz4k]

18 minutes ago, Ape88 said:

I would want this but with a more real life length of time for keeping something warm.

Let´s keep the game challenging, that is why I proposed 2 to possibly 3 hours tops. That can be anything from a long gameplay walk to two big logs of firewood cut down with a hatchet. Time acts in different ways in the game. 2 hours of the day are not that short of a time. 

The idea would be that the hot drink would be finished to replenish "some" temperature while "renewing" the warm core benefit again. I would rather if it was not carried as a "last case scenario save" when the player is already close to freezing, but more as a "prevention" - which actually makes more sense because of that benefit renewal argument which can only help if you are still losing temperature, not once you are already an icicle.

[Ape88]

Then make it a very rare item or make it something that has to be repaired before it can be used.

[Mroz4k]

1 hour ago, Ape88 said:

Then make it a very rare item or make it something that has to be repaired before it can be used.

Do you know what the item actually is, how it is made? If so, how on Earth would you expect to fix it in a survival situation? The insulation is either a plastic, or a vacuum. Once damaged badly, if a wall of the cup got torn through, the vacuum would be gone and you would have a regular metal cup on your hands.
It would have to be a very rare item, obviously. Rarity does not necessitate "more powerful", though.

It shouldn't be easy to carry around heat all the time with ease. If someone can get three of those, that is three warm drinks which mean basically full temperature from freezing to warm (not really but it would be a huge boost).
With a few of those cups, trips to summit, for example, would be laughably easy.

[StrayCat]

That would be a good idea, but I  totally agree with Mroz4k. Don't forget that the weather in TLD is extremely cold, and even a good thermos would not keep your tea warm for many hours, I've seen that in Lapland... 2 hours seem balanced.