Perhaps the RCA CDP 1802 with it’s wide voltage range could be powered from the juices of citrus fruits or solar cells.
If stranded on an Island, you really need to turn the computer into a communication device signalling in Morse, on short wave.
Just my 2 cents.
Assuming I do NOT have electrical power available, but I have some random shipping crates that happen to have what I wished for …
I’d want a manual typewriter, lots of paper and ink, and some dice. I’d make a typewriter tabletop version of Super Star Trek, and other similar classic BASIC games.
See, back in the day, I didn’t have access to a fancy computer. But I did have access to a typewriter. So me and my brother invented typewriter games. They weren’t very good, but we had no idea what the heck we were doing.