How far away are you from Topeka? (It's a bit south of Shipshewana.)
I get all my feed grains from Honeyville Feed. They have non-gmo, likely gmo, and organic choice by the 50 lb bag.
Today's prices:
Corn:
non-gmo $6.85 50 lb bag
organic: $16.21 50 lb. bag
Wheat is high right now don't remember price.
Didn't price Barley or oats but last time I purchased they were about $12/ 50 lb bag for organic.
If you purchase one of the grains that they use lots of, they will usually allow you to purchase by the lb. However, the price is higher per lb. for less than 50 lbs. than it is by the bag.
Prices change based on the market so you have to call ahead and get a price before going and be sure they have what you need. They will usually be able to get whatever you want by next day if they don't have it in their stock.
Their website has not been working properly (this is a small-town company) It may be working better now...
http://www.honeyvillefeed.com/
Facebook:
https://www.facebook.com/pages/Honeyville-Feed-Farm-Supply/129759297072648