I originally tried a Kensington Pro Fit Ergo, but it didn’t last very long. When I went looking again, the MX Ergo had come out. You can adjust it between a more flat or vertical configuration, and it has worked great for me for years now (although since there is a trackball, you do have to pop it out and clean it on occasion). I have had issues with the MX Masters before I switched to vertical mice, so it doesn’t surprise me to hear that you were having issues with MX previously. It sounds like you aren’t looking specifically for vertical mice with a thumb trackball, but I would seriously consider making the switch since you’re using them for ergonomic reasons. It doesn’t take long to adjust to it, and it essentially completely removes the wrist movements you would make with a standard vertical mouse. However, last I looked, there were very few options for that configuration. If you opt to go with a vertical trackball, I would also recommend a cushioned mouse pad for additional wrist support (plus a wrist guard for the keyboard, and compression gloves if you’re dealing with any wrist pain).

I wish you luck with your search!

Thanks for mentioning the last 30 minutes, but for additional clarity, there is a fake ending 30 minutes before the actual ending. Please watch those last 30 minutes!