button to tap the volume regardless of the phone.

Hi @adiueo

Here's a teardown video of the phone that may help to gain access so that you can replace the volume button in the phone. The link is only to show what the part looks like. It's not a recommendation to use the supplier in the link.

Search online for Poco M4 Pro 5G volume button to find other suppliers that may suit you better.

Be careful as a lot, supply the power/volume button flex cable and not the button actuator as shown above. The actuator presses the switches on the flex cable in the phone.