As said you ideally need gen3, most places will have a secondhand hunting market which might have occasional units for sale. There is also the bright LED torch (900nm so invisible to animals) and a normal cheap low light camera…. Used quite widely by hunters as you can build your own very cheaply.
https://www.sionyx.com sell a very sensitive digital night vision system you can freely buy <$1000, but when the dark gets really dark it will stop helping you unlike the real deal which keeps on going till you get to “down a cave” darkness.
In the EU both Photonis and Harder Digital do pretty much the same level of performance stuff as in the US, so you don’t need to worry about importing. Gen4 is marketing hype sometimes reserved for the filmless tech which performs really well in the dark dark, no moon/stars/overcast miles from anywhere type of situation.
When looking at demo images avoid all that are urban/suburban and have any moon about, that is a very bright condition. Milkyway shots separate the good from the not so good. The Huawei P30 pro phone has unreal night performance as does the Sony A7S previously mentioned.
If your aim is to spot warm blooded live stuff I would suggest thermal infrared (same sort of cost, though worse resolution (300 or 600 pixel across sensors) than intensifiers), as they’ll show up far more readily, especially at distance. The pixel size has been dropping over the years and so the cost has come down (can use smaller and thus cheaper lenses). Note this is NOT the near infrared that is filtered from visible cameras, but the long wavelength heat infrared that need special detectors and lens materials. Axion or Helios models from pulsar seem to be good value and reliable.
Luckily we don’t have nasty cold blooded beasties round about, Foxes, badger and deer mainly.
Camouflaged animals that are not moving can be just as hard to spot with an intensifier, though the white vegetation does help a bit.
For wandering about and not bashing things you need a 1x intensifier unit, thermal isn’t so helpful for that application as the contrast is different.
Being able to see in the night really does show you a totally different view of the world most people are not aware of
Peter