The others are right, a 1000-2000w generator will do what the OP ask. Then again for the occasional dry trip with low power usage, I bet the OP already has what they need. A pair of heavy jumper cables. Turn that truck around and run it for a hour or so when the battery starts getting low and you will be fine. A few cheap LED light in place of the most used bulbs would be good too.
Not that any of the other advice is wrong mind you. They are spot on if you really want to set up a dry camping rig. Ours is set up that way and we never have hook ups nor run a generator to charge up the batteries. Unfortunately since we keep one for AC if needed and ultimately as a back up, I have to run it monthly, change the oil, make sure the gas is fresh, store it and make room for it and it's stinky gas can every time we go.