The Daring Dufas wrote:

I can see a little inline converter for the Motorola phones that
would supply the required voltage. A little lump in the cable or
a simple little pod with USB ports on either side that any USB
cable would fit.

It's a simple fix, just a voltage divider with resistors is all that's
needed. But the fifth wire of the mini-USB plug needs to be in the cable
and connected, not just left unconnected since the standard USB plug is
only 4 pins.