is it this chap
http://www.bespokeleathering.com/leather_care.html
taken from e36coupe.com
problem would be matching the colour I would of thought but not to say he wouldn't make one to match
some info here
I would guess that the loom has already been changed for the sony unit. Why do you want to change the head unit anyway, radio? Try a frequency shifter/band expander, Some members have had good results, some poor.