Unless the car left the factory with lumbar support, there is no provision for this option. The only plug-n-play retrofit is heated mirrors; all other options require an additional wiring loom to be installed. Sport seats can be fitted to any A2, but, without an additional wiring loom, the lumbar adjustment will remain in the position it was in when the seats were removed from the donor vehicle.
I've made and fitted countless lumbar support looms for club members and will happily make another for your A2.
Cheers,
Tom