I just found it by searching.
Google 03eb:2ff7 Atmel Corp
Google 03eb:2ff7 dfu
http://www.linux-usb.org/usb.ids
Another way to do it.
~/Downloads/arduino-1.8.5/hardware/arduino/avr/firmwares/atmegaxxu2 $ ls
Arduino-COMBINED-dfu-usbserial-atmega16u2-Mega2560-Rev3.hex arduino-usbserial README.txt
Arduino-COMBINED-dfu-usbserial-atmega16u2-MegaADK-Rev3.hex Genuino-COMBINED-dfu-usbserial-atmega16u2-Mega2560-R3.hex UNO-dfu_and_usbserial_combined.hex
Arduino-COMBINED-dfu-usbserial-atmega16u2-Uno-Rev3.hex Genuino-COMBINED-dfu-usbserial-atmega16u2-Uno-R3.hex
arduino-usbdfu MEGA-dfu_and_usbserial_combined.hex
From the README.txt
Arduino Uno and Mega 2560 Firmwares for the ATmega8U2
This directory contains the firmwares used on the ATmega8U2 on the Arduino
Uno and Arduino Mega 2560. The arduino-usbdfu directory contains the DFU
bootloader on the 8U2; the arduino-usbserial directory contains the actual
usb to serial firmware. Both should be compiled against LUFA 100807. The
two .hex files in this directory combine the dfu and serial firmwares into
a single file to burn onto the 8U2.
To burn (Uno):
avrdude -p at90usb82 -F -P usb -c avrispmkii -U flash:w:UNO-dfu_and_usbserial_combined.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m -U lock:w:0x0F:m
To burn (Mega 2560):
avrdude -p at90usb82 -F -P usb -c avrispmkii -U flash:w:MEGA-dfu_and_usbserial_combined.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD9:m -U efuse:w:0xF4:m -U lock:w:0x0F:m
Did you get it to work?