I keep a solar powered flash in my car, but for casual light availability...
I can't get behind you guys carrying all that extra 'stuff' for a theoretical/maybe situation.
But if 'it' happens I just do what I did the last power outage--turned on my giant screened cell phone.
I've got it with me anyway.
When I first start using a new phone I shoot one snap, overexposed, of a light.
That gives me one completely over-exposed, i.e. empty white, frame which I just keep in the phone's memory.
When I need what would have called for a flashlight in the old days I just turn on the phone, go to that 'picture' and I've got enough light to read a book by, not to mention cook dinner, wash up, and screw around until the electric wonks get the grid gerbil back on the treadmill.
Actually I'm MOST likely to use it in restaurants where the lighting is too low and the menu too dark--that's what made me start the 'white frame' process to begin with.
(Originally I did it with whatever digital camera I had with me, but leaving a white frame on a phone is just simpler and more useful)
Now, if I needed to chase fugitives through the Black Forest..., THEN I might carry one of those honkers.