FIL has a folding bike that lives in his caravan, takes him from campsite up and down whatever waterway he is camped next to to the next fishing spot.
It’s currently go an archaic 1x7 speed system with grip shift and can no longer access all the gears due to the gripshift not rotating far enough around, as well as being a bear to actually rotate. Ive done my best and managed to snag 6 of the 7 gears, but again, it’s not easy to rotate that gripshift.
Thinking a simple swap of a new gripshift/replace with a thumbie or trigger and a rear derailleur will fix it and make it easier for him.
IIRC Halbot had linked previously to 7 speed stuff on the Clickbike site, but I’m not finding much.