Bob's Red Mill. They are close to us and so I can will call the pick up.
If you have a store that sells bulk food, ask them what your price would be if you bought what you want in 25# bags. Most of the time they will sell it to you at a discount. Sometimes you will need to order it from them but at least you are getting it at wholesale prices.
I order from one each month because I prefer organic, but they also have conventional. Additionally, I was buying from a group here local who ordered from Wheat Montana by the truck load until it dissolved. I found that group by a simple Google search.