Fortunately, a lot of internet searching turned up a way in which the Kindle can be programmed to prevent it from switching itself off. Useful for cooks using it for recipes, apparently; certainly useful for FIL during the night when he wakes up and wants to read further without requiring anyone else to turn it back on. It means that the Kindle needs charging every few days rather than every week, but that's not a problem.
So Kindle holder number 3 is a lightweight affair, made from thin plywood rather than mdf, and with cutouts wherever possible to keep the weight down:
This is now in use, but tends to move too much when the page-turning buttons are pressed. So we are adding to the mix a lightweight plywood tray with some anti-slip material attached which FIL can position on his chest in bed under the Kindle holder. Laborious but, we hope, effective.
If you have limited grip and digital control, managing toilet paper can be tricky. Don't worry - not too much detail needed on this one. Just a simple wooden shelf which holds the moist wipes boxes in place by friction, so that the lids can be pressed open and the tissues pulled out, without the whole caboosh ending up on the floor:
Last for now, a couple of further arm-crutch holders for different places in his flat. We call them elephants' feet, and they are simply made out of 110mm drainage pipe, which is surely a stock item for most people?