AFAIK, the closest to these specs is the
Tekplate. It's not a plug-in, but a replacement outlet cover with a built-in 4AAA, 5led amber light. It has a sensor that monitors the electromagnetic field around the wires. I've seen this advertised with a 48-hour runtime. Switch plate models are available in amber or red. I think the switch coverplate might be a better idea, as it will also mark the exit in an emergency.
There's also
this upcoming power failure led light from Topcom. 3 power levels.
As far as I know, most led power failure lights are also nightlights. I've ordered
these for use in the bathrooms in my house. As an aside, I've been using nightlights for the bathrooms for about a year, and the main bathroom lights are no longer left on all evening. I think the nightlights provide sufficient lighting for quick bathroom trips, and the main bathroom lights only get turned on when we're getting ready to go to work/school or go out.
ledmuseum has a review of a similar nightlight/flashlight/power failure light
here .
The links above were selected for the pictures and info, not the best prices.