Well I believe only the FBX file format is going to support opaque data, so if you have an FBX exporter in Cinema 4D, you would need to check the docs for the exporter or contact the maker of the exporter to determine if the exporter supports creating the opaque data. If the exporter does not support it, then I would think you could write your own tool to insert the data using the free FBX Software Development Kit from Autodesk:

http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=6839916

You would have to develop your tool in C++ however. Otherwise you could consider switching to a content creation tool that does support it such as Maya or 3DS Max. A third option would be to alter the NormalMappingModelProcessor so that it gets the texture filename from another source.