This Pedal is currently available.
Line Mixer
The Micro Line Mixer is a 4 input stereo mixer that’s small enough to fit on a pedalboard. It’s ideal for creating parallel or wet/dry/wet guitar rigs, or for any place audio signals need to be combined.
https://www.rjmmusic.com/micro-line-mixer/
Included in 5 Pedalboards, 1 are public:
RJM Micro line mixer
RJM Micro Line Mixer
RJM MICRO LINE MIXER