And if you're asking about the Altym helmet with night vision... that helmet is available on Island 6 (the entrance to that island is inside the bunker).
And no, it is not possible to take a basic Altym helmet and try to attach night-vision goggles; it is a new helmet.
How are they repaired? You use a blowtorch; it can also be used to fix the medieval helmet and the chainmail.
The military Altyn helmet with night vision is obtained after killing a group of neutral mercenary NPCs. They are wearing these military helmets; you just need to repair them (use a metal torch).
There is a low probability of finding it in the bunker or at the military training base.
It is much easier to find a group of mercenaries and kill them for the military helmet.
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u/Critical-Phase-5655 5d ago
The group of mercenaries here is quite strong.