The BeBook Mini/Astak PocketPro/Hanlin v5 have a nice scrollwheel on the side that is very light to use. You don't need to use any force to use it, just brush your finger alongside the edge.
The other device that you might want to look at is the Sony 600. It has a touchscreen that also allows the use of a stylus (beside a finger, so a nail should work as well) and that should work for you. This is a 6" device.
(Nate has a nice video on his blog on the difference between capacitive and resistive screens:
http://www.natesebooknews.com/2010/0...h-screen-tech/)