To get a reaction from someone, you may have to provide additional information to help identify which Greiner you mean. Are you referring to Hermann Greiner, DOB 02.01.20, who was last living in Wangen, Germany? If so, then you may want to e-mail the Gemeinschaft der Jagdflieger (GdJ). Their website address is:
www.fliegergemeinschaft.de (
http://www.fliegergemeinschaft.de) . You can also post a request on their web site, I believe.
If that's not the right Greiner, then you may have some difficulty since Greiner is a relatively common name in Germany.