i wasnt't aware of the "Panning Law" which totally makes sense...
I found this passive stereo solution. But i assume the Panning Law is not respected:
https://myvolts.co.uk/product/82800/myVolts_Pots_and_Pans_-_potentiometer_volume_control_with_pan_mode_and_mute_button
it shouldn't be that hard to solder short cables with jacks of your choice onto this PCB...