Don't worry about an extinguisher - CARRY A SHARP KNIFE.
I well remember being trapped in a car for 30/40 mins (it was remote area) until the fire brigade arrived. The two front seat had shunted together so you couldn't access the release.
Have also seen someone suffocate when trapped upside down in their harness. (A bit like the way crucifiction works, after they break your legs).
The main reason we don't now need a fire crew at airfields used for ab initio training in the UK is that these crews have failed to save anyone for 60-odd years. Basically, you get out, or you are dead by the time they take you out.
Get a knife and be one of the ones who get out.
And always brief your passengers about where the knife is too.