On the way to HC '05, I got stuck in a 25 > 30 mile traffic jam.
Just started going over a bridge and the next exit was 3.9 miles away.
90 miles gas left shown on the OBC. Shut the car off, coasted etc. and made it to the exit with 8 miles gas left on the OBC.
This prompted the gas can search. I remember a BMW one long ago and it is still available. TUV approved too.
Surprising part is that there were eight of them in the USA. This can holds 2.36 gallons and fits in a 15 inch or greater wheel well. To make it secure, I had to securely mount the wheel to secure the gas can to the wheel.
Came up with a unique tire mount kit. Tire mount kit is $75 priority mail shipping with tracking included.
For adding the gas can I made up a Delrin insert that goes through to the floor and accommodates the bottom of the gas can with the foam ring on the bottom of the can mating with the wheel ring. It is then secured to the wheel using a coupling nut and rod using BMW standard spare mounting pieces.