I have a surplus un-mounted fire extinguisher mount from the group buy that happened a few years ago: Official: GB: Quick Release Fire Extinguisher Mount
$45 net to me by PayPal, buyer pays shipping from SoCal/90039.
Thought I'd post another "Wheelchair Mod..." -This one for quick access to an extinguisher:
If you have short & tall drivers...this might restrict how far forward you can slide your seat (though you can take the extinguisher off if you absolutely MUST slide it way forward. It uses the mounts...