Buying a Wonder Box Cooker

You could also google "solar oven" and go from there.

I did Google this and came up with several wonderful instructions for making not only the Wonder Box but also for other types of solar cookers. This would be wonderful for camping (maybe for Boy Scouts too) or just for times there is an electrical outage as well as for difficult times, such as storms.
You can also find places to purchase this as well. I did not check out those sites so don't know prices.

I didn't look long enough to see if there is one for purchase, but, if you Google 'wonder box for cooking' you will come up with directions for making one as well as instructions (recipes) for use.