FYI, this PCIe to M.2 cable works for me to install an NVMe drive in the CX770: https://www.amazon.com/gp/product/B07TKYMQXZ?psc=1
Plug into the PCIe slot, bend cable down behind the CPU (it will not fit nicely), twist the cable 90 degrees halfway, and the M.2 module lands on top of the left...