When im not lightly geared for an astronomy session, i consider my laptop to be an invaluable tool for observations, plus i find it extremely difficult to locate abell planetaries without it. But even if its a portable encyclopedia, i find it very disturbing when i have forgot to dark adapt the screen and have to waste an extra 20 minutes to achieve night vision. Usually I use a combination of low brightness / black-red desktop theme, which is a very nice way to have your eyes protected from light, but needs preparation from home in order to gain some time for your eyes. Some years ago a friend from Special Forces had told me of a simple way to dark adapt a flash light by using red plastic transparent sheets for presents or candies so why not use it for a laptop screen? Even with a default white colored theme and brightness at 100% it didnt broke my night vision and at the same time i was able to find everything in my programs without blinking. I use a 14″ laptop so I used a A4 transparent (try to get a clear one) envelope for papers and notes which i usually bring with me, with some blue tack.
Sorry for the image quality but i hope that point taken.
In case the red plastic sheet is not an option (or you want to use both options) you may try some linux/windows based themes that can be found in some sites.
Gnome/XFCE : ClearLooks Black – Red
Well i basically use dwm and stumpwm so my themes are custom in level of status bar/modeline.
Finally for Micro$oft Window$ users its not hard to create one of your own. Just set everything to black and fonts to red.
Also i’ve read somewhere that starry night software has such features that apply to global desktop colors. Kstars or Xephem and Stellarium have something similar that applies only to the program frame.
In the same way you can upgrade and use an old flashlight. Why spend 25 dollars for a special uber featurefull astronomical flashlight just to look cool (come on admit it..) when you can make one by yourself?! Keep the 25 bucks and gather up for more eyepieces! To make a red flashlight use some of the red plastic sheet to the flashlight to cover up the bulb/led and tie it with some rope as shown below. If the white color glare is too much, just put some extra sheets and tie them up.
Another option is to paint your flashlight bulb, red, with nail polish paint, or get a red bulb/led to replace your white one. If you try the nail polish option keep in mind that it might need several paint layers (5 or 6) to get it to be as red as it needs.