Looking at the Reed Instruments manual, it talks about "An USB RS232 lead." There is no such thing and the reference to RS232 might be wrong. It looks like it might really a USB connection with the two wires being the D+ and D- of USB 2 or USB 3.
It looks like they sell an expensive cable to connect to USB. It is not clear if this has any electronics or is just a phono plug to D+ D- cable. You could make one by splicing old USB cable to an old phono plug cable.