Getting auto gas at airports

There seem to be a lot of people using auto engines on their
homebuilts. I am a low-time student pilot so pardon me if this is a
stupid question, but do many airports have autogas available at their
pumps?

If you're doing cross-country flights, seems like it would be a huge
problem if your refueling stops didn't have the kind of fuel you need.

If airports don't have autogas, what do you do in this situation?

Thanks,
Patrick