Contour Rollermouse FTW
Because the cursor movement is by your fingertips resting on a horizontal roller you move without moving your arms, and use with either both hands or whichever is your dominant. So you position a compact keyboard like a Bakker Elkhuizen toward the monitor(s) with the Rollermouse nearer you (and get the one with the deep wrist rest or you'll need to add one), and you move your hands forward and back just enough to use either device.
No, I don't work for them, but my employer kindly paid for me to have a workplace assessment when lateral epicondylitis threatened my work capability, and this is the solution they provided. It worked for me (Yay! No more pain!), and when I retire in a few years Contour will get my money for a personal purchase, not Logitech, although I'll always have a soft spot for them.