The Pololu DRV8835 Dual Motor Driver Shield for Arduino can be purchased on Pololu's website. Before continuing, careful reading of the product page is recommended.

DRV8835_library This is an Arduino library created for easy use of DRV8835 breakout from DAFR Electronics Tested and working perfectly with DRV8835 breakout form DAFR Electronics: ...

However, for the prototype, he uses a SparkFun SAM21 Arduino-sized board, a Pololu DRV8835 dual motor driver board, four photoresistors, two motors, a battery, and sundry other parts.

However, for the prototype, he uses a SparkFun SAM21 Arduino-sized board, a Pololu DRV8835 dual motor driver board, four photoresistors, two motors, a battery, and sundry other parts.