Keeping food cool requires either an ice box or a mobile fridge.
I have had a number of ice boxes. Initially I used some light weight plastic style boxes which worked OK but I ended up with a heavier fibre glass and foam Evakool box made locally on the Sunshine Coast. The Evakool boxes are more durable and I think are better insulators. There is no reason why you cannot use an icebox in your camper – you just need to plan around replenishment of your ice supply. Bag ice is available from most service stations and large supermarkets.
I also had a 3 way fridge that I purchased from Aldi. I never used it on gas but did run it from the cigarette lighter in my car as well as on 240 at caravan parks. It worked fine but struggled to keep a low temp when temperatures hit the high 30s during the Queensland summer.
For the camper I was seeking a fit out with a built in fridge and was tossing up the decision to go with a recommended 80 Litre Dometic fridge (Coolmatic CRX 80 model) vs a smaller 60 or 50 litre version. I initially thought that installing a smaller fridge would give me additional shelf space or might gain more room above the fridge for a drawer eg for knives and forks.
Then when I was talking with a work colleague who had been driving her VW camper for 10 years – she told me that the fridge was perfect general storage space. So that was the end of that.
That is where I will store the first aid kit, dry foods and more.
The next size up is not really an option in a SWB Transporter as it is around 10cm wider which reduces the available storage cupboard space a bit too much.
Choice magazine has a buying guide for portable fridges.