I found a Great little 600 Watt "Pure Sine" inverter that is very affordable and well crafted. It comes with two sets of cables to connect it to your camper and it includes a Remote Control Switch.
I tested it out on my "Big Screen" TV (55") and my 10 year old JVC Sound system and it ran both flawlessly.
I then tested it out on my smaller 29" TV and new Sony sound system, with DVD player, we use when camping and it powered both without a hitch.
For my test I used my 9ah Battery Jump Box to power both tests. The 55" big screen and JVC Sound System ran for just over an hour.
The 29" Camper TV and Sony Sound system played DVDs for a little over three hours using the same battery Jump Box.
Based on my test, I estimate that 3 hours of TV and DVD usage with the smaller system uses approximately 5 amp hours of battery capacity.
Here is the link to this Great little 600 Watt (1200 Watt surge) Pure Sine Inverter: