The refrigerator should be smaller that the one used in cars/boats (in order for example to be kept into a rucksack when he does scouting). Should be rechargeable-battery powered and be the size of a medium-book. I think that using peltier-effect should be possible to build small devices (of course, just to cool a small volume, for example 3/4 syringes). I think the device should be for specific healt-usage.