Apparently, only one or two were built. Some details are here:
http://www.turnkeyrc.com/bf163.htm
There was also a small book by Hans Justus Meier: "Verbindungsflugzeug Weserflug Bf 163, D-IUCY." Flugzeug-Monografie/ VFW-Fokker Nr. 3, published around 1970.
Ed