1. you do not show your location so I assume you are willing to send the camera anywhere on this planet to get it serviced.
2. International Camera Technicians http://www.ictcamera.com/ list Graflex in their list of cameras that they service.
3. http://www.baldmtn.com/AINFOSHT2.htm has been reported as S L O W on http://www.graflex.org/ .
4. Fred Lustig, a gentleman in his 90's, has been repairing Graflex Corp. cameras for years and has parts. He is available by telephone only so be aware of time zone differences when calling him. He is in the Reno, NV. phone book.
5. I service Graflex SLR's and Graphic Press cameras. I have no experience with the National Graphic nor any service information. I would take a look at your camera if you can find no other source for repair.