Suitable low-power ~10" graphical display options
1000 mAh / 0.8 / 12 hours = about 100 mA, which is plenty. A parametric search on DigiKey landed half a dozen monochrome LCDs (Display Modules - LCD, OLED, Graphic), and they're all expensive ($200). First on the list is DMF-50036ZNBU-FW-BAN, which draws 30-40mA. I wouldn't recommend getting any of these as they are expensive, but you may be able to source similar ones from China.
I meant to put this as a comment to the OP, but I don't have the points yet.