Me grandmother passed away in her sleep and I always thought how lucky she was to have gone that way.
I think many of us would hope to pass in our sleep.
Anyhow, as far as a contraption to induce this, I unfortunately don't have an answer. Of course, some drug overdoses would lead to death in ones sleep. I had surgery recently and the best part was going under anesthesia. Total peace when I was under. Makes me wish I had the tools and resources to administer my own anesthesia and end it that way.
I suppose "N" is viewed as a type of anesthesia, or in a similar light. I understand the appeal, for sure. Once during one of many inpatient stays, I told the hospital psychiatrist I wanted to be put down, put to sleep. We don't let our pets suffer, why are we forced to linger in agony? Any compassionate person would help to end the suffering of another. At least, I used to believe that.
I have lost faith in psychiatry and the mental health "industry". Keeping us alive at the cost of our sanity.