This 7 inch 1080p HDMI Monitor is 12 volts because it’s designed for use in cars, but I think it’s too good a deal just for entertaining in your car. It also has audio. Below is a battery that works well with this monitor. This monitor and battery combination is recommended by my friend Stu Sweetow (avconsultants.com).
7 inch 1080p HDMI Monitor
Portable Power Bank and Car Jump Starter
This battery may be overkill, but it will do the job handsomely. How many hours would it power the 7 inch monitor above? Stu rigged an adapter cable to plug into the standard round 12v power input on the monitor. It has a Y adapter so he can power his 12 volt mic mixer and monitor at the same time.