If this helps in your search, here are the part numbers from my 2009 Mk6 GTI's rear halogen lights. It's a right hand drive (UK) car.
Driver's Side Tail Light: 5K0 945 258
Driver's Side Tail Light (Boot Hatch): 5K0 945 260
Passenger Side (Boot Hatch): 5K0 945 259
Passenger Side Tail Light: 5K0 945 257
I upgraded from the above lights to OEM LED Dark Cherry Rear LEDs (upgraded my BCM at the same time to ensure compatibility due to it being an early Mk6).