craigslist always has them in varying amounts from what I see.

You could ask at a garden center if that is the type you mean? I would just tell them about your project and ask what they would charge, they will prob just offer them.

Any building sight should have them or go to Freecycle.com.
You can also drive around and find them in trash pickup.

Landscaping companies possibly could have some available when they do their final site clean up and bring the used empty pots back for disposal.

Thanks guys :) I found some pots.

Wish you were closer. I have about 100 1 gallons I need to get rid of.