I’ve ordered a couple of these from this listing: https://www.aliexpress.com/item/1005002988965317.html
In the mean time it looks like a very simple drop in replacement:
- Remove the keyboard from your DevTerm
- Remove the screws from the back plate of the keyboard
- Remove the keyboard backplate
- Take out the scroll ball package
- Drop in the new scroll ball package
- Re-assemble everything
The scroll ball package just sits over this little sensor/button