That time traveling hippies are in short supply?
(Oh c’mon ------ someone else has got to remember Idaho Transfer)
There are self-winding wristwatches that store mechanical power from your movements. Would it be possible to have an arm powered by generators run by your other functioning muscles (like your legs and/or other arm?)
Yes, the other limbs would have to work harder than you’re used to, in order to run the generator, but maybe it wouldn’t be prohibitive?