Dear Mr. Cunningham,
Thank you for posting your request on History Hub!
Also, the German War Graves Commission (Volksbund Deutsche Kriegsgräberfürsorge) has the database Search for the burial place of your relative! and although this is not completed yet, it is not clear if it includes casualties whose burial place is unknown.
We hope this information is helpful. Best of luck with your family research!
There is a military mailing list https://list.genealogy.net/mm/listinfo/militaer-l
The list is actually in German, but many of the participating people there speak English. I read there for several years and there are some very knowledgable and helpful people. This list is from the main page of the German GenWiki page http://wiki-en.genealogy.net/Main_Page
Records of German soldiers are available here: