How does one add a commutator to the UCLA miniscope cable?
I'm one of the developers of the Miniscope. We have been very happy with #FL-2-C from dragonfly. This commutator is very low torque and we have never had an issue with sending power or data through it. The key is to minimize the length of non-coax cabling coming out of the top and bottom of the commutator. We trim the lead wires short and solder coax connectors to both ends of the commutator.

For a slightly cheaper option you can check out the commutators sold by MOOG. I should mention that we haven't tested these with the Miniscope system yet.