Where can I buy a finished mobile camera module?
How about: 

https://www.sparkfun.com/products/8667
which has a full datasheet on the site.

Also, most electronic distributors such as mouser or digikey will have datasheets of all the products they sell. For example, all the cameras here have datasheets.

A good example to use to look for how to interface to camera modules is the CMUcam source files: http://www.cmucam.org/, which is an open-source computer vision module using the Omnivision cameras (the CMUCam4 uses the OV9665, the CMUcam 5 uses the OV9715). Take a look at the source files to see how they read from the cameras.