When I fitted a sunroof in my old 110, I used door seal rubber. I split it lengthways and then fitted the part that clips to the door frame on to the roof lining, then opened up the now split tubular part and tucked it into the groove in the sunroof, fixing it in place with a length of the rubber filling strip from a windscreen rubber. It cost me nothing as it was all leftovers from my kit car building days, but I remember it came from a place in Tunbridge Wells.