You are pretty much stuck with e10 91. However, we measure octane differently here in the US, taking two test methods and averaging them. Some countries use only one method, and the one they use yields the higher number. So if you are only looking because your owner's manual calls for 93, don't sweat it.
https://blog.brocksperformance.com/f...atings-so-low/
Phoenix area fuel comes from L.A. refineries via pipeline. Tucson gas comes from a TX refinery, so perhaps you might find something different there. I know fuel is generally less $ in Tucson.