Did some checking into this last year. There was a Sunoco in Troy that carried it but since I live near the Oakland International Airport I looked there....and BINGO! That's what piston driven aircraft run on. I stopped at several hangars and asked around. One said NO, two said "no problem, just bring gas cans" and one said "just back your car up to the fence and we'll call for the truck to fill it up". Just for clarification, it's not "No Lead" but instead it's 100LL (low lead).
Moral of the story; if you're near any airport check with the hangars. The planes need fuel and it's 100LL so give a shot. Most they can say is "no".