I've looked at the "adaptive equipment". The only one that looks interesting to me is this one: E-Z Fret. For $12.95, I might buy one myself just to try out, even though I don't need it. It doesn't appear to help with the problem of fingers that can't be used, though. I would think it would work to buy several and have them in other positions, not just first.

I have a couple of other ideas and I apologize if they seem a little far-afield:

A problem with the acoustic guitar is that single-note playing sounds a little thin. I think people tend to play the things that sound good on their instrument and avoid doing other things. Wind instruments don't sound thin with single-note playing and I started to do more on the guitar after I started playing trumpet. I think that happened because I recognized the possibilities of it and could imagine the way it could sound, even though it still sounded thin.

I bought an oud not too long ago because I wanted an instrument without frets with a guitar-like range. I'd already had a fretless bass guitar for several years. I always used to say that violinists, violists, cellists and contrabassists were just too cheap to pay for frets, but I'm finding it very addictive to play the fretless instruments. It opens a whole new world and you really learn to use your ears in a different way. And chords don't work.

Another possibility is a bouzouki. They are _loud_ with lots of overtones and single-note playing doesn't sound thin. I have a three-course one and the typical style is to play the melody and often use the other two courses for rhythmic accents on the open strings. I definitely recommend this, too.