I sent Dave a text about this, maybe he can chime in and confirm it. There is a Renegade Race Fuel hub in BG just a few miles from the track. They go by Valor Oil.
407 Raven Avenue Bowling Green, KY 42101
My friends go there (or at least used to) to buy E85. It's very consistent and not much more than pump 93.
If for some reason they don't have it there anymore, you can go south on I65 to exit 97 in TN and there is a Shell station that has it. But, that's almost an hour drive.