Get SunTour thumbies and operate in friction mode. That's what I do on my mountain bike.
Would barcons be a suitable option for you?
As you are seeing, nothing compares to the simplicity and robustness of friction shift, and once you get used to it, indexing does not offer any tangible benefit.
__________________
"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069