I didn't see this mentioned. Forgive me if it was.
Firegone foam extinguisher
We used to carry these on Blake's store, but they're available everywhere, including Home Depot, Walmart, etc. AND CHEAP!!!!! $12 to $15 at most stores.
According to the literature, the foam is non-toxic and non-corrosive. (Those terms are relative... don't eat the stuff, and don't use it in place of LPS 3.)
I've sprayed one at the shop and it seemed quite satisfactory. And easy to clean up. And didn't suffocate me. And it stays where you spray it, mostly, aside from some run off.
In flight, you could spray the fire... or spray it on your legs, hands, etc. if the flames were encroaching on your skin. That is something to consider.
The only down side to this type of extinguisher is that they WILL FREEZE in cold weather.
I have no skin in the game here, but I do think that I'd prefer a foam over ABC every time. And over Halon in most cases, simply due to the high cost of Halon.
YMMV. Fly safely!