I buy 100 octane low lead aviation gas from our regional airport. There are a couple of fuel suppliers and both will sell to walkin customers.

I only use it for my 2 cycle equipment so a 5 gal can or 2 is all I buy at a time but it is easy enough to buy.

K1 is cleaner, cheaper, but doesn't burn as hot so you use more. Most of my life we used K2, that's what everyone sold. (this is for a stove with a chimney, not a portable heater)

When the Stewart's convenience store chain came to the area, they sold K1. We bought it because it was there. lol They were open late and it was cheaper. I don't think it even dawned on us that it was K1 instead of K2. For a long time I couldn't figure out what was wrong with the old stove. I even started to look into finding a replacement carburetor for it, I figured there had to be something wrong with it. "I have the carb turned up to 4, almost 5, we should be baking!" This went on for a couple winters until the "duh" moment when I realized I wasn't buying the same fuel. So much for the savings.