Pocket Operator mixer for seperate line recording

Hey guys!

Can anybody suggest the best way how to record synchronized pocket operator separately (that i have each PO line recorded separately)?

I would love to do a final mix and master on computer. Otherwise I have only one track and there is not much possibility to mix and master it.

I found this mixer prototype https://youtu.be/65kMYklLS80 but can find any ready made one.

Can somebody help / suggest the best way how to do this? And what gear is available out there?

Sorry for my bad English, hope you can understood the question / problem.

Thanks in advance!