It is called brake pedal switch bumper. Made of rubber. Mine was broken after 8 years. The parts can be seen scattered on the carpet.
1st step, I went to one accs shop and they replaced it with a bolt and nut. Paid RM5 for the job.

Not feeling comfortable with metal hitting the plastic switch everytime so I went to SC to replace it with the actual rubber bumper during a periodical service.
Forgot how much the thing cost but should be around RM10~20 for a small rubber part.

Probably you can buy it cheaper at the spare parts shop and replace yourself.

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