Sympathy and empathy for your pain, Rafiki. I have de Quervain's Tenosynovitis, which causes pain at the base of my thumb and also nerve damage from ulnar compression.
A Shimano Di2 drivetrain is one of the most popular electonically shifted drivetrains (SRAM is another), but a full conversion would be expensive.
One of the less expensive alternatives currently on the market would be the Archer Components D1x. It is a an electronic "shift box" that shifts your rear derailleur only. It is brand- and cable travel-agnostic, as it can be programmed and fine-tuned with a smart-phone app. Supplies are limited, cost is purportedly USD$389. I don't have any interest in the product, but did see a live demo and it was impressive. Shifting is by two handlebar-mounted buttons, one for upshifts, the other for downshifts.
As mentioned, it shifts only the rear derailleur, so is intended for 1x systems with just a single front chainring. I can't see why it couldn't be fitted with a 2x (double) or 3x (triple) crank; it just wouldn't shift the front, which could still be selected manually for greater range.
Link here:
https://www.archercomponents.com/video here:
https://www.youtube.com/watch?v=5nZYF2SdTfI&feature=youtu.beUser installation videos here:
https://www.youtube.com/watch?v=EMtkPktAzXIhttps://www.youtube.com/watch?v=vgIUmDFOrlwAt present, it appears battery life may be a problem, at least compared t Shimano's Di2 system, as it is rated at 30-hours in the normal mode, and 50+ hours in the low-power mode.
Pinkbike review here, comments are interesting:
https://www.pinkbike.com/news/archer-components-wireless-electronic-shifter-review.htmlBiukemag review here:
https://www.bikemag.com/gear/tested-archer-components-d1x/There are some problems, including the use of 1.5mm socket allenhead screws used in setup and for battery cover retention. That looks problematically small over time, but time will tell. Depending on the length and width of a bike's chainstays, some people's heels have hit the shift-box. The button control is not as ergonomic as some other button-shifted designs. Though the actuator batteries look like AA cells they are not; special rechargeables are required. It uses a carbon-brush motor rather than brushless or stepper, but the maker says it is rated for a high service life). I have no idea how it will work long-term and it is expensive, though less so than a complete conversion to a electronic shifting (depending on your current setup; it appears this could even be made to work with a freewheel and friction-shifted rear derailleur). Although the Archer system uses buttons, they still require a push-push motion like Rapidfire, just with less effort and travel. You might be able to mount the shifter buttons so you could use an index shifter instead of a thumb.
Happily, I found my Nomad's T-bar mounted grip shifter (which I approach from the end, as I would to turn a doorknob) causes me little if any pain compared to other shifter designs. Perhaps converting your present bike to a compatible derailleur-type GripShifter mounted on a T-bar might also be a helpful alternative? Bar-end shifters cause me no pain, and a pair of them could be mounted into each end of a larger diameter T-bar like this one:
https://www.sjscycles.co.uk/accessories/thorn-accessory-bar-mk2-t-shaped-105-mm-extension-254-mm-0-deg/?geoc=USJust some thoughts.
Best,
Dan.