I used to have an old Apple Macintosh SE30 in the darkroom. I masked the screen with ruby lith tape (over the monitor bezel, not directly on the glass) and it worked fine if I turned the brightness down. Poor thing gave up the ghost in a poof of smoke one day.

If you could disassemble your pocket pc and place a piece of clear plastic with ruby lith tape over it and sandwich it between the display and plastic case or otherwise affix it without sticking tape all over the display.. you'd be golden.