Several members have raised this subject in the past, particularly when having despaired of blocks, wedges, pillows and other contrivances.
Here is one I found which appears to be a well made, multi-position W-function metal construction.
£549 on Amazon or from the Swiss supplier (mattress extra) seems to be a reasonable investment in getting sound rest and avoiding the danger of inhalation pneumonia.
There is a cheaper non-electric version.
[ I should stress that I don't own one or have any other experience of the product]