The Espresso Mart on Signal has a corn-free sign on the 93 octane pump.
If you want to verify what your buying is corn-free mix follow these instructions from The Hull Truth:
The only testing kit you need is a cheap plastic baby bottle from a dollar store. Fill with water to 50 ml line. Add 150 ml fuel, to bring mixture to 200 ml line. Mix well. Wait a few minutes for water and fuel to separate. If water line is still at 50 ml line, you have Ethanol free fuel. If the water line has moved higher than 50 ml, there was Ethanol in the fuel sample.