These are overkill for your requirement (they offer several hours of runtime) but these have been the most successful for me - with a half dozen installed at friends & family over the years:
Discover the ultimate solution for home safety with Ideal Security rechargeable emergency lights. Perfect for power failures, our LED emergency lighting fixtures are battery-operated, ensuring your home is illuminated during unexpected outages. Shop now f
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I bought them via Amazon in Canada but apparently Amazon in the US does not offer them.
Oddly enough I had problems with a 2-head version I purchased, since AFAICS the electronics are pretty much the same.
For something smaller (eg plugged into a bathroom outlet) I had pretty good luck with a Lee Valley light that looked a lot like this:
Much less light but fine for a small room, and easy to pick up & use as a flashlight.
EDIT - it's probably obvious, but one of the reasons I favor the first light for friends and family is that they probably do *not* have a bunch of flashlights sitting around in known working order, and there's a good chance that this will end up being their primary light source in an extended blackout. I encourage friends/family to also have a couple of outdoor solar lights that can be easily brought in at night as a source of at least getting-around-the-house light in case power stays out for longer (my power was out for a couple of weeks recently).
For most of the people on this forum, however, I imagine a power outage might be met with a bit more enthusiasm, and the primary requirement for a power failure light is to help you navigate safely to at least one flashlight. Sort of like when you hear a warning that roads are bad and everyone needs to stay off them... and you think "woo hoo !" and go looking for the Jeep keys.
Still, it would be nice to have a flashlight with enough reserve power to run my well pump.