I don't know where you can get it locally, but when I was researching making the mechanic bar, I saw a couple people mention using cornmeal. I don't know if you would be interested in that or not.
I found a distributor in Houston. I called and they said yes they have it and yes I could pick it up. I'm waiting to hear back from the email I sent on pricing.
I had went to the website of CR Lawrence and looked at their list of distributors and found one called D&F Distributing inc