You should try to buy something with light. You can close it if you don't like it but there are greatly different than the backlight of tablets. It is certainly possible that they won't cause headaches. You should at least try one from a friend before making a decision.
I recommend Boyue T62. Or if you don't want to import, this one:
http://194.33.112.113/~icarusre/open...ory&path=82_86