Get yourself a 120 watt solar panel or there abouts and a baintech battery box.the baintech will run a 40 ltr Engel for 3 days before needing a recharge and in conjunction with yr panel will see you sorted for long stays as well. We sell them at Battery World.  

The baintech is a 100 amp deep cycle battery with Anderson plugs usb and 12 volt connections also has the capacity to jump start yr car if stuck, they weigh in at around 30 kg. 

Just going through the same thoughts for running a fridge on the boat . Don't want to run it off starting battery but I do have 2 batteries with a switch but they are not deep cycle batteries .

Ebay. 160W panel should handle your fridge, Just need a 100-130 AH battery.

Fridge will draw 4-5 a/h half the time so your panels will need to be able to put in 10-12 Amps when they are working.

Worth remembering that at this time of year, with shorter days, the usable sunlight is down so the more amps going in, the better

 I have 120watt solar panel for my Waeco CF 60 and I got it on ebay for $175 from Victoria. Same ones in the shops start at over $400. Had it for a couple of years now and works fine. I also have the Waeco battery which will run the fridge for 48hrs without charge.

Hint - the box the panels came in I cut of the sides and put them in the carry bag on the outside of the panels and used it to protect the panels when packing in the car. 

 I had a 50 Waeco and 120W panel with MPPT controller plus a 120AH AGM battery.
I found that the 120W would not quite run the fridge continuously over a long period but part of this is because the panel on the boat cant follow the sun and experimenting at home by moving panel 3 times a day it could (roughly 40% more power generated)

I have since swapped to a 70L fridgemate Evakool, and even though it has the same compressor as the Waeco and more capacity, it is a fair bit more efficient for some reason.
Seems to easily keep up as long as it stays sunny.
Bitdeals Ebay for panel, $200 delivered, 3 years and still works a treat.
Best current at midday sun is just touching on 7 amps according to my clamp meter and the gauge I installed

I run an Engel 60ltr fridge/freezer, a 120W fold up "Rich Solar" panel (best for when you need to track the sun) and dual 120AH Deep Cycle batteries in the truck, works ok but need to watch ambient temps for fridge, not so good in temps nudging 40c or more.

I might get a 3rd battery.

Can always  just go for a short drive....exploring, whilst charging both batteries...

EDIT: I reckon the best way to help keep the power usage down (battery drain) is knowing EXACTLY how to keep everything at the right temperature, you need to know how your fridge works. My only fridge I have been using for the last 4-5months is my 60ltr Engel, only because i'm too lazy to fix the other one :)

Yes depends so much on what your doing. following the sun on 20 degree days with your fridge on 5c in the shade ? Or pumping 45 up north no tracking putting warm beers in to 2c?

My 40l engel would run forever on a 120w panel with a 130a battery doing the first scenario. on the other hand the second scenario is what i actually do on the boat and i have 250w running into 300amps!

Do you drive everyday ? if so a good dual battery would do. I second rich solar they are cheap and good just get a better mppt reg!

 Awesome advice thanks guys!