Quote - I want to add support for a pull-down menu to choose a realistic camera profile.

The lux documentation says:

Quote - LuxRender contains camera data for a small number of cameras; these can be chosen as a preset. It is also possible to supply your own camera model if you happen to have this information available as a .dat file.

Where are these? I don't see any in the LuxRender application folder.

Did they mean LuxBlend, not LuxRender?

http://src.luxrender.net/lux/file/f98eef13b6d6/cameras/realistic

You can grab them from the source repository. The LuxRender app does not include them probably because it is up to the exporters to make use of them.