Before I got the Lee hand primer ( both old style & new style) and the LCT press with the primer lever I used an RCBS Ram Priming unit I got in the mid 80s. It is a setup like a die that sits in your press & you would be using the lever of your press to do it, rather than your hand/grip strength.
It looks like this:
Source & more info:
http://rcbs.com/Products/Priming/Too...ming-Unit.aspx
You have to put the primers in one at a time with the RCBS Ram Prime unit, but you have to do the same to fill the tubes, if ya use the Bench-type RCBS one to load it up, so it is still something you are going to have to do with your hands either way.
The only way I can see doing anything that doesn't involve much fine motor skills with the hands & fingers is the Lee on-the-press units, like the Lee Safety Prime, & Lee Auto Bench Prime, where ya simply place the Lee Safety/Auto Bench Prime primer tray over the primer tray with the primers in it & flip it over to load up the Lee Safety/Auto Bench Prime Units, close the cover & latch it & then prime either on the press or on the bench.
Those are my thought & suggestions anyway. I have neurapathy in both my elbows, forearms & hands, as well as inflammatory and gouty arthritis & although I still use the hand primes on occasion, to keep up the strength in my hands & forearms, I still have the RCBS Ram Prime set & the Lee Safety primes to fall back on when I reach the point where I cannot use the hand prime, just like the situation you are in/approaching.
G'Luck! whatever ya decide to do & I hope it works out well for ya!