You should (as suggested up-thread) check out the marinas. There are a buncha them within, say 50 mi of Annapolis.
Also look at https://www.pure-gas.org/
Also I was able to get a 5gal can of racing fuel (lead free 100 octane - $60 though) at a local fuel distrubutor’s base operation.
What is the octane booster in ethanol free?