First of all, you must be living in a strict area, because I've been going out for a while, and I've got a young face, and I manage to get into quite a few places. Secondly, don't bother. They're cheap, and they're illegal. You can get into a lot of trouble if one of the bouncers is moody and passes it onto the police. It's serious business. No proper fakes can be found online, just crappy ones that any bouncer can tell they're fake.
Finally, it's much easier just to borrow a friend's ID who is 18 that you can pass for. Safer and simpler, if you get rejected then no sweat.
4 months isn't that bad either, I'm 18 in 3 months exactly today, and I've managed, although it has been annoying quite a few times.
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Intelligence is the ability to avoid doing work, yet getting the work done.
Treasures await...