Was just there yesterday for a visit and looking for my ancestors graves. Have had the same problem you have but contacted Kevin Frye at fyre@pstel.net regarding information concerning them. He was a great help. In addition, his wife works at the visitors center there and is also a helpful. Don't know if you've use the nps or ancestry.com data bases in your search but may also be of aid.

Michael J. Cone, M.D.