Like most things in life if your pockets are deep enough things can be done. Kufatec do the harness to add seat heating (Seat Heating - Harness - Audi-38961_M) however as you will see you will also need to change the climate control panel and add a number of other components. It may be that Audi fits the heating elements as standard to all cars just does not enable them unless you spec them. There was talk a while back of Audi adopting a policy of including options within the car but not enabling them. Not sure how you would check though. There is another option however, seems to be the same solution one as a kit (Audi Heated front Seat Kit - Carbon Fibre) and one installed (Aftermarket Heated Seats | Heated Car Seats Installation - AVS Manchester) for you.