Like Chris said, get an ARB or Engle fridge/freezer.
They are built for expeditions and camping tips, and do not draw much amperage.
They can go four to five days on a single automotive battery without starting the rig.
I ran my ARB for around four days on a long weekend with it in my rig, and I did not drive anywhere.
It started right up to go to work.
Here is a link to the ARB one.
Here are two of my installations.
PS, I know these type of fridges are on the expensive side, but they are well worth it.
They have other uses as well.
Last winter we had a power outage at my home.
I had no idea how long the power would be out, so I turned my ARB fridge to freeze, and put perishables from my freezer which was worth at least a good $200 or more, and put them in the ARB out in the rig and turned in for the night.
The home fridge alone can keep the contents in the main compartment safe for a day or so, but the freezer can "warm up" to above the safe temp to keep frozen goods at a safe temperature.
The ARB fridge saved the day so to speak.
Power was out a good 24 hours or more,
When it came back on, I brought the food back inside.
I also bought my fridge from forum vendor TRD Parts 4U, and will called the fridge down at ARB since I work down the street from them.
The fridges are worth every penny.