Just came across this:
5 Inch Touchscreen Galaxy's Thinnest GPS Portable Navigator - GPS-C3250
5" LCD, touchscreen, GPS, FM, thin, and ebook support (only TXT, but for 5" it would be fine.) Plus, it's Win CE 5, so other stuff can presumably run on it.
The battery life is 3 hrs, but that's with the GPS running. It should be longer if the GPS is off.
I didn't notice resolution numbers, maybe they don't show them for a reason.
Anyway, I thought it may interest some because of the TXT ability, and the price is close to that magic $100 number.