I think I should point out that carrying a standard fire extinguisher like those you see laying on the ground in front of the driver side tire at car shows will be next to useless if you actually have a fire in your vehicle.
I've always carried fire extinguishers in every vehicle I've ever owned since I had an under-hood fire on a '68 Camaro in college. I was at home and put it out with a big blanket that was in the garage.
A couple years ago I had an electrical fire in a vehicle. The fire extinguisher like the one in your photo will last about 10 seconds before being completely emptied. After that, if the fire isn't out, you're out of luck.
I'd suggest carrying a fire blanket instead of, or in addition to, the essentially useless fire extinguisher.
