If you're handy with a soldering iron, it's pretty easy to make an adapter. Solder a 500k ohm resistor between pins 4 and 5 (ID and GND).
You'll need the following parts:
- A microUSB headset adapter with all 5 pins, like this one on Amazon.
- A 500k ohm resistor
- Knowledge about the pinout of the Micro-B usb connector. Wikipedia describes it pretty well.
Once you have them, follow these instructions:
- Open up the headset adapter and take a look around. If you ordered the one linked above, you'll find pins 4 and 5 connected by a solder bridge, but if you have a different one you may find a something else, like a resistor.
- Desolder pin 4 if you need to.
- Solder the 500k ohm resistor between pins 5 (GND) and 4 (ID).