The whole problem is not so much the 2A charger; rather, it's the USB cable being used.
I have not got the skills, but am convinced that all the cable is doing is presenting a resistive load across some of the USB pins that is detected by the Vox, and that this then informs the Vox that this is the correct charger.
For an example of another device and it's cabling requirements, take a look at the cable for a GARMIN Nuvi GPS
For 2A chargers take a look at The Source. For instance I see this LENMAR ACUSB31
that is 3.1A USB charger.