Chris from the Welly Cruiser Club can get 2 KG fire extingishers pretty much at cost for $56.20 Quote "These are good ones with a bracket that wont let the bottle fall out even if you are upsidedown!"
If you want one for your truck email him at
chrisg@hayandgibbons.co.nz , perhaps if enough people are interested then he can get it cheaper thru bulk buying.
A 2kg one is better than a 1kg one ...... more volume ... Ask Hosehustler he carries a 5kg one

, if you already have one then consider having the 1kg at the front within easy reach and the 2kg one in the back of your vehicle.