Where to get fire extinguisher?

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I've never had a fire on a car myself but having just witnessed a friend deal with one I'm getting some extinguishers.

My buddy has a Boss 302, he had the air cleaner off and the car was running, he did not notice the fuel bowl leaking and when he revved the car up it back fired and instant fire. Another fellow came by and poured his soda drink on it, well the drink spread the fire and it was a nasty situation. Fortunately not much happened.

I need to get a few in car extinguishers. Is Halon still the hot ticket? Any recommendations on where to purchase them?

Thanks in advance.