Just a quick post today to mention that Aldi, the well known German supermarket chain which is known well for stocking eccentric things, has Airbrushes in stock as of today (23/7/16). I got up bright and early to get mine, but I needn't have feared - my local branch had about forty of them, and I was the first person to buy one. And that's at a small branch in the country.
I have not had time to test it yet, but it is actually a double action unit, which surprised me a bit. The airbrush, compressor, and all required gear costs $99.
They are also stocking airbrush paint (black, white, and the primary colours, plus some metallics), and various hobby tools, such as a sort of knock off dremel-y thing, dremel-y thing bits, and laser-cut wooden models of the Cutty Sark and HMS Victory.
Huzzah for Aldi! Long may their eccentric habit of stocking things like wheel-chairs, reconditioned Xbox Ones, and wooden toys persist!