I know that years ago Testors had their own line of airbrushes that, from what I understand, were fairly decent and weren't going to break the bank either. I don't know if they still make them or if they are or were all that good but it might be worth checking out though. There's also a brand called Pasche, I believe that they make good airbrushes and they offer a whole line of them from beginners to experts.
What you might want to do is to do a general search for airbrushes and take down names and model numbers of airbrushes that look appealing to you. Once you've done that do a search for reviews on those airbrushes and see what you come up with, that should help you narrow down your choices.