Try joining the "Germany-Passenger-Lists Mailing List" - there are several members that are like bloodhounds when it comes to finding passengers that you can't find. Be sure to search the archives in case any previous threads are helpful to you.

http://lists.rootsweb.ancestry.com/index/intl/DEU/GERMANY-PA...

Their home webpage is "Germany Roots" - look for the forum wheer some of the same people post and reply: http://www.germanyroots.com/