Happy New Year Lawrence. I just went to Amazon.ca and used the search "airbrush gravity feed". Here is the link:
http://www.amazon.ca/s/ref=nb_sb_ss_i_0_16?url=search-alias%3Daps&field-keywords=airbrush%20gravity%20feed&sprefix=airbrush+gravity%2Caps%2C465
Lots of results. You indicated you were on a budget. Temptation would be to go with the lowest price option. Although cheaper airbrushes might outwardly look the same, machining and tolerances are quite different, yielding drastically different performance, results and longevity. I would forgo the purchase of a few kits and invest in a good brush (Badger, Paasche, Iwata). Some may boast about what a cheap deal they scored, but ultimately you get what you pay for. Quality is not cheap, nor should it be. Surprisingly I did see a link on eBay that clearly shows that Tamiya has teamed up with Sparmax for a gravity feed gun. Tamiya is a name linked to quality. Also, Sparmax I believe is the company that private brands Iwata compressors. I know, more food for thought to add to your decision making, LOL. Good luck with your search. Personally I started way back with a Tamiya SprayWork System (trigger style). I now have Iwata, Paasche, and Sparmax airbrushes.
P.S. I still have my good old Tamiya SprayWork System. Up until recently, I still used it in my classroom when I did my year-end model building sessions with my Grade 5 classes.