I suppose my suggestion depends on what you’re going to use it for: everyday filling, or medium-term gasoline storage. If you’re looking for everyday filling, I have no bright ideas to offer.
If it’s medium-term storage and occasional filling that you’re after, I’d consider 5-gal. closed-head metal solvent drums, of the kind used by laboratory and chemical supply companies. If you work in a laboratory and order 5 gallons of flammable solvent, this is what it comes in:
They’re cheap ($10 – $20 each), very rugged, and made for transporting and storing highly flammable liquids. They are stackable, and the threads are designed to accomodate standard spouts, hoses, hand pumps, etc. I’ve seen them in red.
Downsides: they are not designed for eronomic comfort, they are usually not vented, and since they are designed to be used indoors, the protective paint layer is thin; once scratched the metal would probably rust if outdoors. I imagine several extra layers of protective coating applied around the base would easily solve that problem. Although they would be more than sufficient for containing gasoline pressure under normal conditions of temperature fluctuation, commerical gasoline containers are equipped with an emergency venting device in case of extreme temperature increase. Also I doubt they are approved by state fire marshals for filling at gas stations.
This place seems to be selling some for $12.75 each. (Note the "UN rating," noted at the bottom of the page for this container: 1A1/Y1.4/160, which exceeds the rating generally used for transportation of gasoline (UN 1A1/Y1.2/100).) Always check this rating.