I'd add that Heet! (yellow bottle never red) is also available in general stores, mini marts, big box stores, gas stations, auto parts stores, and even the tiny automotive section at many grocery stores. It tends to come in what I find to be a more convenient size container than alcohol at hardware stores and marine supply stores. Heet! comes in 12 ounce bottles which I find to be just right while at the hardware or marine supply store they often have it only in quarts or gallons. 12 ounces lasts me 4 days to a week or so depending on how much I cook.

Also in a pinch, while not ideal, alcohol stoves can burn rubbing alcohol in a pinch. The heat output is less due to the fact that it is usually 30% water, but if you don't have anything else you can get by.

Additionally some folks burn grain alcohol like Everclear from a liquor store. Too expensive to suit me, but it is an option.

So far Heet! has been available enough that I have not needed to resort to anything else.