Most natural gas generators are orderable for propane. Propane delivery is available most places, although you also need to find a place for the tank. It's more convenient to have fuel delivered via pipeline, but somewhat less resilient (although I personally don't have any experience with outages of utility natural gas, it is a possibility).

Based on the one ~ 3 day outage I had, my whole house generator's tank is good for probably close to two weeks, although if it were very hot or very cold, that might change. I have a portable generator for my well, that one runs on gasoline and doesn't sip fuel, I'd probably just run it for a few minutes twice a day (did not have that generator during the 3 day outage... we were just stinky)