Ladies and gentlemen. 15 years of experience here with boat / camping car fridges.
You want 5 days of fridge without charging, yeah?
Two solutions.
The long-term cheapest solution is to buy an 'A' class bog standard household fridge freezer, running off an inverter, 1000 watt (it's the pull on the compressor starting up which it needs), the inverter needs to run off at least one heavy duty deep cycling ideally AGM battery, two in parallel, better.
Even better, two heavy duty AGM in series running a 24 volt inverter, halving the amps.
12 volt fridges cost at least 4 times the cost of a 240volt jobbee, and have a limited lifespan.
Off the top of my head, a 12v half decent fridge freezer is £800.
A 240 household 'A' class £150?
An inverter £200 max, doesn't need to be pure wine wave. We use COTEK, highly recommended.
If it's in your car/ truck/ camping car, you can always run the engine a bit to top up the batts.
At work I run 14 boats, with various 12 / 24v systems, an inverter allows you if you need it to run anything else ie phone/ computer e.g. Chargers off the same system.
Split domestic charging systems also very useful.
Does this help?
Arent AGM batteries really expensive?