You can try Bass Pro if there's one nearby. They don't have it out on the floor, but check with the gun sales staff. Usually kept in a container in the back. You can do better online.
I went by the Bass Pro in Atlanta and also one in Birmingham and they both had none. The one in Atlanta told me that Goex went out of business (no joke) and Bass Pro no longer carries black powder due to the cost of the license.
I could buy online but I really wish I could buy in less than $100 increments.
Is that with, or without hazmat and shipping fees? Last I checked, it was $15.99 for Grafs name brand, and they were mostly out of stock. With shipping and hazmat, the price goes up fast, unless you plan to buy bulk and spend a lot anyway.