And don’t forget, also
I think you’re getting somewhat confused attention because people miss responding to one or more of your list of requirements.
How big is the storm shelter? Are the walls and ceiling painted white?
And, again, are you willing to wait the 20 minutes or so — maybe twice that — for dark adaptation?
Remember any brief use of a brighter light (including a screen) will make the room appear much, much darker until dark adaptation is reestablished, under your moonlight source.
Are you willing to use a 2- or 3- or 4-cell light?
If you get one of the fairly common emergency lanterns and use rechargeable C or D cells, it might take care of the problem, although not in the precise way you want.
Here for example: https://www.dorcy.com/950-lumen-area-lantern
(40 percent off with code CYBER right now, and they frequently offer big discount codes — and have very good support online)