Built my own today. Hidden for daily driving and seat back for CAMS track days.
Great idea, I think every car should have a fire extinguisher, just in case. In 40 years of driving, I have used my extinguisher three times at accident scenes. Maybe didn't save a life, but certainly prevented a lot of damage.
I love the idea of it being hidden under the seat, but may be hard to get out if your car has lost power because of a fire, and no-one knows it is there except you. It might be handy if you are unconscious, and your N is about to go up in flames for it to be visible.
Because I am cheap, I made my own bracket also. I bought a 1m length of 50mm by 5mm aluminium, cut a 500mm piece, rounded both ends, like this:
Bracket 1.jpg
Cut two more pieces from the rest, and made two brackets that look like this:
Bracket 2.jpg
Attached them to the mounting plate using countersunk bolts and nylocks, sanded, primed and painted the whole thing in gloss black, then attached the bracket with the the same bolts and nylocks.
Looks like this:
Ended up shortening the horizontal arms of the angle brackets, and mounting them underneath the seat rails, rather than on top inside the rails, as they don't impede the seat movement that way.
$20 in materials, spray primer and paint I had in the shed, and 1 hours labour.
Geez, I charge $95.00 per hour for my time. I should have just bought one from Hyundai! LOL, It was therapeutic at least.....