RaztheDestroyer: There are night-vision military headgear in Krasnoz - armour trader. Traders/caravans will rng them also.. for me about lvl 12.
ladyonthemoon: They don't work, do they? I just bought one, used the "use" fonction and put it on but I cannot see any difference.
They reduce (or eliminate?) penalties for shooting in the dark. But they don't do anything visually AFAIK.
To visually light things up, the miner helmet from the dead city is the (only) way to go, strangely enough. The only problem is that most people (myself included) don't go there till near the end of the game, since it has some of the toughest enemies, plus the toughest fight in the entire game, and most people (again, myself included) don't want to pay the $6K or so in travel costs more than once.
As you probably already know (since you could afford the NVGs), $6K isn't really anything to worry about, so if you really want them just go there, find the subway, there should be a shop that sells them. Either that or just roam the subway system and take one off a dead stalker.
BTW I haven't tested to see whether enemies see you easier due to the massive beam of light coming off your head, but I assume wearing these helmets wouldn't exactly be "stealthy".