I dont think BMW do a retrofit for the nav screen im afraid you can do a DIY but it certainly isnt for the faint hearted and would need to be pretty clued up with electronics. You could ask mikethemini at
www.newministuff.co.uk he might have done one although im unsure....
I had the Nav in my ONE and wasent too impressed with its functionality to tell you the truth thats why I opted out of the BMW nav screen for a kenwood 725 motorized one IMHO the kenwood is the daddy
