Is there a Microwave Cooker with a Safety Cut Off

[sarah_louise]

My mother has mild dementia and no matter how many times I explain still puts food inside the microwave within foil trays or other unsuitable things.
Today yet another magnetron was burned out.
We are excellent customers at Comet or Curry's for microwave cookers of course.
What I wondered was the possibility of finding one that would cut off automatically ?