What's the name of this part inside the Rival?

I recently did a RMA on my Rival 710 which required me to break off the mouse 1 & 2 buttons by peeling them off the mouse and snapping them off completely.

I decided to completely disassemble the mouse and would like to make a guide showing that process for the Rival 710 (Would most likely work for the 700 as well, since they are very similar).

I’m curious if anyone happens to know the name of this part that the mouse buttons were attached to, and if anyone has possibly seen a place to pick up another one short of ripping it out of another mouse.