This Module is currently available.
RK003 Passive Mixer
Passive 8x stereo mini-jack mixer to 1x stereo mini-jack out or vice-versa (split 1 stereo channel to 8 out) Each port has a 100K resistor to it to protect audio signals from each other. Synch signals should not be bothered too much with this small resistor value.
These merchants probably sell this module. Huh?
Retrokits Retrokits RK-003 Eurorack