I have a couple of the 22oz MSR fuel bottles around. They are 2-15/16" diameter, which is just a tiny bit fatter than a normal water bottle. The straight portion of the sides is about 6-1/4" tall before it starts to curve inward.
The above MSR fuel bottle is about 1/16" fatter than a normal water bottle (since its aluminum, it won't compress at all like the plastic water bottles do). Because of the fatness, these bottles will not fit in many bicycle water-bottle holders--but I think it is the one that comes the closest. So you may have to get one of the bottles, and then just be prepared to take it along to the bike shop and try fitting it into the different water bottle cages they sell.
Plastic gas cans are made of polyethylene, so any polyethylene bottle should work. The aluminum water bottles would probably work well too, except for the fact that they're not labeled as intended for fuel. I'd bet that all 50 states of the USA now have laws saying that gas stations cannot let you dispense fuel into a container that isn't marked as intended for fuel, and that's where the advantage of the MSR fuel bottles comes in. The text printed on the bottle actually says it's intended for flammable fuel, so the gas station people can't much argue with you on that issue.
I also posted here a while back that I left some gasoline in one of my MSR bottles for a year or so, and the plastic cap swelled up so much that I could barely unscrew it without breaking it. After I got the cap off I poured the fuel into another gas can and left the bottle & cap open for a couple weeks, and after that, the cap screwed in properly (quite easily) again. So you might want to only use the MSR for keeping fuel in when you're riding, and pour out the fuel into a regular gas can after the ride.
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Also we note: I ended up not using the MSR bottle, as I switched to carrying another (much larger) gas can.... but I don't think I have EVER seen a water bottle cage that I couldn't lose the water bottle out of, when hitting big bumps. I always got the "extra-tall" water bottles and then used a piece of shoestring to tie around the thin portion of the bottle and through the frame-side of the water bottle cage, to make sure that the full water bottle couldn't fall out.
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