Retrofit Computer

[Popell]

About to take delivery of a 2005 1200GS, wire wheels, three seat options(!) vario panniers and top box (all soft inserts too), heated grips, ABS,charger - all done only 2200 miles from new!!
I know the vendor and it is a straight up deal.
My question concerns the possibility of retrofitting the computer functionality that was an option when new - was it a factory fit bit of kit or is this possible.
I have trawled through the forum without success so starting the thread.
Look forward to hearing of any of your experiences
Regards
Pope