I recommend going to tcpglobal and checking them out. http://www.tcpglobal.com/airbrushdepot/airb9.aspx
You need to make sure the airbrush machine is food safe.
My machine is from a hobby shop/toy shop. My Dad bought it for me as a gift. I've never used anything with it but edible colors. I then bought a small "donut" air compressor with a regulator so I could control the PSI. My whole system cost about $300. I agree that it's a little pricey but I didn't pay for it 
and every single piece is metal so I love that I will/should never have to replace it.
But, yes, you can get a airbrush machine that isn't from a cake site.
Cake decorating airbrush system with a set of americolor colors cost 129.99 at amazon. And you can find multi purpose airbrush for 79.99
I have looked for special food color but no one around me seems to sell anything other that what I already use? I got one from Harbor Freight for my birthday with a compressor for less than $100. I use vodka and add my gel colors. Hubby cut the side off a big box so I can spray inside the box so the over spray dos not get every where. I keep any left over color in a small plastic bottle.
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