@Aremis @Fawkes Read up on a topic before complaining about it. Pair programming is a real thing and not used to save hardware. Telling people “your boss sucks” isn’t helpful.
@OP Your employer doesn’t seem to understand the concept though, because pair programming doesn’t need two mice/keyboards. The idea is that one person writes the code and the other one only looks at it.
I don’t know about configuring two mice on a PC, but you could try to find a mouse which allows configuring what the individual buttons do. This way the mouse will also work should you ever want to work on a different PC.