NRW2705

Hello there, I picked up my Sept 2012 registered A5 yesterday and was gutted to find out that it doesn't have a DAB digital radio. It seems that this only came in as standard on the post 2013 models. My own fault I thought it was standard from 2012. Does anyone know if it is possible to ad the DAB Digital radio module to my audio system and if so what the cost is likely to be? many thanks in the hope someone can help