It may be that the only difference is the connectors that plug into the controller, but I don't know whether anyone has tried changing the plugs.
If the USB chip is the same, it should be possible to either modify a cable by fitting both connectors in parallel
(or make up a simple plug in adapter) to allow a single cable to be used to program either controller.
HPC300 programming lead:
VEC300 programming lead:
If someone can post some close up pictures of the wires and connectors used for each controller, it might help to determine the common connections.
I'm guessing that the same four wires
(Red, Blue, Green and Yellow) will connect to the USB PCB on both leads.
Alan