You should be able to adapt one of the Jeep Wrangler carriers- check Quadratech... I think that's where I got the one I used to have.
Gas cans inside are safer than outside, BTW. Outside, they can be crushed in a simple rear-end accident and dump fuel, static electricity is HUGE on the outside of a moving car too. But if that's what you gotta do, that's what you gotta do.
