Hopefully this cable will come with the controller. From DJI's web page: "Supported USB port types: Lightning, Micro USB(Type-B),USB(Type-C)™"
I've also found it on B&H site - $8, not available yet:
DJI RC Cable for Mavic Controller (USB Type-C)
B&H # DJMP5RCC MFR # CP.PT.000561