Borgward Owners Clubs
Another excellent source for finding those rare parts for your classic Borgward is through the various owners clubs located around the world. Many clubs have exclusive new parts sources, having commissioned manufacturers to make obsolete parts that are in demand. You will normally have to join the club in order to take advantage of this supply, but the small registration charge could be a great investment & save you an awful lot of time!!
Also, some owners clubs have discussion forums and an ads page where members can advertise any parts that may be surplus to requirements. Interaction with owners club members could also lead you in the right direction to locate the elusive Borgward parts you need.