USB C, HDMI Switch for MacBook Pro/Mac Mini
Keyboard and mouse only

Only taking into account the keyboard and mouse you can perhaps use software to share those with multiple devices instead of hardware.

Synergy can do this, but is currently paid.
The last free version is 1.8.8 and is available at sourceforge.

Screen, keyboard and mouse

Alternatively you can access one machine (e.g. the Mac Mini) via remote desktop from the other (e.g. the MacBook Pro). If they're on the same local network and depending on the use case the speed should be very acceptable.

I'm not affiliated with Synergy, just a happy user.