As noted, the OP is in ZA.
Solution: buy a locally made, for him, National Luna and be done with it. Yes, they are "pricey" compared to other models, but, as with most things in life, you get what you pay for.
NL fridges and freezers are consistently ranked the best of the best. They are well made, super efficient and will literally last a lifetime. There is no better solution than one which solves your "problem" for 20 years straight. Buy once, cry once and be done, instead of cobbling something together or buying a bunch of imported, off name brand garbage.
People have become so price sensitive, that they can't see the forest for the trees. Does it make sense to buy a cheap Chinese solar panel, inverter, battery charger, batteries, wiring, MPPT solar charge controller and a household fridge that is not designed to go bouncing down the road in a truck, when you could just buy a high quality, efficient, long lasting fridge?