http://www.dizziness-and-balance.com/images/master-ear.jpg I've ordered a pair of standardized silicone ears from a manufacturer in the US, who has built his own binaural dummyhead for recording purposes. The ears cost me $129.00. Apparently I could've made my own but the cost of 5L of silicone (smallest drum available) is 1K so I made the split decision based on the investigatory nature of my project.
If you're interested in the process of building a dummyhead recording unit, check out Jeffrey Anderson's guide here.
Ears are one of the most important aspects of a dummyhead recording unit, as they shape incoming sound waves before they enter the ear canal and reach the ear drum.
A major component of building a successfully working dummyhead is understanding the physiological process of perceiving sound. Readings by Daniel Levitin, This Is Your Brain on Music, and Oliver Sachs, Musicophilia, offer a great deal of insight into physiological sensing of sounds.
Additionally, understanding the fundamental properties of sound, it's potential in all objects and the physics involved in the creation, movement and reception of sounds is critical. The Fundamentals of Hearing, by William A. Yost is a great starter. It provides a methodical progression on the basic properties of sound waves, typical impacts on waves as they move through space, and the physics behind sound localization (like HRTF, for example).