If you have a flintknapping group near you, that's the best place to get some flint.
Most of us will share with you in person, but a lot of us don't have all that much and we put a premium on our "stash". I'm not sure you would feel you are getting enough rock if you trade.
With that said, just let us know what you can trade. Many of us would like to get our hands on high quality arrow shafts made from hardwoods, for example.
Ebay is a good place for flint or obsidian if you can't get it locally.