Contact any seed dealer and they will tell you where a local grower is in your area that raises Indian Corn.
You have to make a deal with the grower as many of them have all of the corn pre-sold each harvest. I made a deal with a feed store in New Mexico about 17 years ago and have been buying it from them every year. It is a process to get the product, but well worth the effort. This stuff really works, as I've set up 2 feeders side by side and every time the deer will eat Indian Corn 1st. Folks make fun of me about this, but with all of the products out in the market for deer, somehow Indian Corn is over looked by many.
In many ways it is fine by me, as it just makes my experience in the woods that much better. But spend some time on Google and you will end up with it if you choose to try it.