I have 2 compressors, both cheap Harbor Freight products. One is the small airbrush compressor. The other is a small pancake compressor I bought for pumping up tires etc. Want a better quality one for airbrushing my models. Budget not set in stone...thinking around $200....but could go up.

I'm very happy with the Artlogic AC1418 I have. Fine with My Iwata HP-CP airbrush and old Badger 160.

I got it from an Aussie supplier:
https://www.hobbytools.com.au/artlogic-ac1418-super-quiet-mini-air-compressor-with-tank/

$189 AUD. That is a little less than $150 USD plus postage on that. Not sure if you can source more local.

I have the same one from the same shop,very happy,small and super silent

in US they are branded "Masters" and sold here...
http://www.tcpglobal.com/Airbrushing-Supplies/Compressors_4/

The best is probably this model with cooling fan..
http://www.tcpglobal.com/MASTC-40T_4.html

I got a Sparmax compressor at Hobby Lobby. $349; but if you download their app to your phone you can get 40% off one item.

Oh yeah, I burn those 40% off coupons up. 3 Hobby Lobby stores within 20 miles of me. Just hit two of them yesterday and grabbed some Tamiya primer.

I am really happy with a 20 lbs. CO2 cylinder. No power needed. portable, silent, lasts all year and easily refilled. No water spatter, won't wear out. If you can get past the thought of "I have to have a compressor" then it is a perfect solution.

So I went out today and picked up a 20 lb co2 cylinder and regulator because the pump diaphragm wore out in my air compressor. When I started airbrushing the tank had about 1000 psi, but after about an hour later it was down to about 875. I was spraying at 18 psi like I've always done with my compressor, but when I noticed the rapid drop in tank pressure, I lowered it to 10 psi. Does this sound right because I begining to think that this tank wont last a month.

For that amount of money, you can easily swing a 10 or a 20 lb CO2 tank plus regulator. Amazon has them, of all places. I bought my tank at a welding supply store, and my regulator was a spare my lab had when I was a post-doctoral fellow.

With CO2, you never have to worry about humidity getting water into the air hose, and thus never needing a water trap. You also don't have to worry about the noise a compressor makes.

"So I went out today and picked up a 20 lb co2 cylinder and regulator because the pump diaphragm wore out in my air compressor. When I started airbrushing the tank had about 1000 psi, but after about an hour later it was down to about 875. I was spraying at 18 psi like I've always done with my compressor, but when I noticed the rapid drop in tank pressure, I lowered it to 10 psi. Does this sound right because I begining to think that this tank wont last a month."

Don't worry. The standard CO2 pressure is near 800 to 1000 lbs. depending on the temp. As long as there is liquid CO2 in the cylinder, it should stay at/ near 800-1000 lbs. If there is no leak and you are using an airbrush, the tank should last a loonnggg time. I turn off the main valve to the tank when not in use.
If you were using nitrogen gas, the pressure would be near 3000 lbs.
What were you spraying? An hour is a lot of spray time if you were constantly painting.

I was just laying down a base coat. Thats probably about an average time for me to do one.