Need air Conditioner on 1st floor window.?

Question:Our Bedroom window faces the street in NYC and we need an AC unit. Problem is we do not have a window guard that is built to accomodate a bulky unit. Are there REALLY thin units out there to fit in small areas or a cheap gate that we can install ourselves? The stand alone units with the exhaust hose are not a good option for us because space is limited and they are very bulky.

Answers:
Only the rear of the unit needs to be outside. make/use a small table to rest the unit inside the room so only the rear is sealed by the window.