Have you heard of MSR fuel bottles? Camping/outdoor stores sell them.
The 22oz MSR fuel bottles will fit into some bicycle water bottle holders, but not all. They are the right height, but are a tiny bit fatter than a regular water bottle is. They're spun aluminum, so you cannot "squeeze them in" if they're a bit too fat.
This is the normal type of wire cage they will NOT fit into:
Nashbar Sport Mountain Water Bottle Cage
They may fit into the side-wrap-style cages, like this one-
Nashbar Sidewinder Cage
They may also fit into the split-type cages, like this one-
Ascent Butterfly Road Water Bottle Cage
One advantage of the MSR bottle is that it actually says it's intended for flammable fuel right on it. US gas stations aren't supposed to let you pump fuel into any container that's not intended for it. The gas-station clerks have a tough time arguing it's not a gas can when it's red and has "fuel bottle" and a bunch of flammability warnings printed right on the side.
One
disadvantage of the MSR bottles I've found is that leaving gas in them a long time may cause the cap to swell and be difficult to unscrew. The bottles are really intended for camp stove fuel, which is usually kerosene, that has no alcohol in it. Gasoline in the US now has alcohol, and my guess is the alcohol is what causes the cap to swell after a couple weeks. Just don't leave the gas in it more than one day, and it works fine.
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