Odds are you won't get a decent one localy, most local places sell party foggers, which the quality lacks on. If you have a local theatrical supplier, they should be able to help you, or do the BMI, Production Advantage, etc... thing. For foggers, most people go hands down either a g100 or a g300 from lemaitre. Rosco also makes a decent fogger. The G300 is nice because it also can be a hazer of sorts, not a great one but a hazer none the less.
I am from the Philly area, so I know every company around. Starlite Productions is very big in this area, have a hold on just about everything. They are in Cherry Hill, NJ. There is also Earl's Girls in Egg Harbor City, not as glamorous as Starlite, but will try and beat Starlite's price on anything. Then there is Mainlight and Light Action in Delaware. Another company I work for is a dealer for Elation which makes so descent foggers at competative prices. I'll send you a PM with links and what not.
I'm going to bump this topic to get some more advice on for machines.
I looked up the g300 and it was way beyond my price range.
What are some good units for around $500.00? What all will I need to buy to run it from our tech booth (we have some "on-off" dimmer channels for DMX applications like fog machines and bubble machines, etc.).