This is a common problem for Google Pixel 7 Pro phone (Volume button fells off)
Google community thread https://support.google.com/pixelphone/thread/190978264/pixel-7-pro-volume-button-fell-off?hl=en
XDA thread https://www.xda-developers.com/google-pixel-7-volume-key-mishap
Designed with trial and error
Because I lost the button, I measured the "hole" and start designing it
The author marked this model as their own original creation.