Any kind is better than nothing!
ABC dry chemical are the cheapest & what can be found at most general stores, but that powder in them is very corrosive to electronics & makes a huge mess (but still better than your truck burning to the ground). Carbon Dioxide extinguishers are great & no big mess; however the plastics horn type nozzles are kinda bulky. The best is halon (older type) or halatron (new fancy more enviro friendly version) a clean agent that is perfect for our vehicles, but expensive too.
Personally, I have an old halon that was taken out of service ... price was free, because it would have had to been disposed as hazardous waste now since the extinguisher company will no longer service them (stupid EPA regs). So it is technically no good, but reality is it's still charged & will work!
If you have a fire extinguisher servicing company in your area, I'd ask them. Sometimes they have used extinguishers for sale (not pretty & shiny but have been services/inspected) or may have an old clean agent you could "dispose of" for them
