compressor

I don't know if this is helpful, but I purchased a small garage type compressor for my model room.  It fits under the desk and is a piston type, which pumps into a holding tank (or pressure vessel).
The regulator draws off the holding tank (holds about 10 gallons, I think) so there's no "pulsing" feed to the airbrush.
I can spray for about 5 minutes continuously before I have to fill the tank again.
I got the thing from a place called Bunnings (in Australia)....a great big hardware warehouse (anything like Home Depot?)....it was only about $100....and even if it dies next month (I've had it more than a year) it's still been very good value.
I could have spent $600 on a dual pump, silent unit specially designed for model use - but I didn't see any point.
This one is pretty loud - so I just switch it on, leave the room and close the door.  It only takes a couple of minutes to fill the tank, and I've got a silent, continuous air supply.

Well if you dont mind getting a larger and less quiet one, do what I did. Go to your local hardware store, Walmart or Sears etc... And buy a small compessor. They sell them to run small nail guns or to air up tires. I paid $70 dollars for one and it works fine, although it is loud. Make sure it has a pressure regulator so you can adjust the air pressure. They are a little bigger than an airbrush compressor about the size of a 20 inch TV or a little bigger. Hope this helps.

Well Leemitcheltree beat me to it. LOL Anyway this sounds just like what I have.

Ive got one thats about 4 gallons i picked it up at pep boys for 45 or 65 bucks  i cant remember its made by coalman.

Here is an alternative to think about.

For about $150.00 U.S. you can get a 20 pound CO2 bottle, pressure regulator, and water filter (trap), plus the necessary fittings for attaching your airbrush. The CO2 is inert and non toxic. This set up is perfectly quit, easily portable, and inexpensive to operate. I get my bottle refilled about once a year at a cost of about $20. The spray pressure is consistent, that is there is no spitting from the pulse you get with most of the hobby airbrush compressors, and there are no moving parts to wear out. Understand that you are renting the bottle and when you go for a refill you simply exchange your current bottle for a refilled one. If you rent your bottle from a local Gas Supplier then you generally must get your refill from the same supply company. A 20 pound bottle is about 8 inches in diameter and stands about 30 inches tall. The bottle can be steel or aluminum. I prefer the aluminum tanks because they are a little lighter and do not leave a rust stain on the floor or carpet. 

I have had a series of the 1/10 HP hobby compressors and they usually last about a year before the bearing siezes or the diaphram develops a pin hole or a crack. They also spit because they are a "pulse" type compressor. The larger compressors are generally noisy and use a lot of electricity. I have a 10 HP compressor with a 60 gallon tank in the garage. I thought about running a 1/4 inch line into the basement for my hobby use, but the compressor is noisy when it refills the tank, and with a 220 volt line it uses a lot of electricity ($$$). I work on my kits late at nght, especially on weekends, so the compressor noise is a deciding factor for me.  All of the suggestion above are good ones, but I thought you might like another alternative.  

ok cool. thanks for the help. i was thinking about trying an auto parts store and havent had time to get over there. now i know its a good place to go. thanks again. hopefully now i can get some models done and put some pics up.

Wal Mart carries a few good compressors and a few that come with tanks. The Cambell Hausfield compressor is pretty good... comes with air regulator adjuster, PSI guage and just about any air brush will work with it. The Cambell Hausfield starts at $50.00 and the downside of this compressor is it is loud.

Air Master