This replacement switch button is for the original Mastermind, Mastermind LT and Mastermind PBC products and can be used to replace broken switches. Replacement requires disassembling the product, but does not require soldering.
This video shows how to replace the switch actuators in a Mastermind PBC/10:
https://youtu.be/fogulsBal6A
The process on an LT is similar, but easier (there's only one circuit board to remove).
Mastermind PBC10/LT Switch Actuator
RJM Switch Actuator PBC10 / Mastermind LT
Canada Tone Design