If you are just interested in the mass-attenuation coefficient, as opposed to the mass-energy absorption coefficient, then you can can simply calculate it based on the elemental composition of hydroxyapatite and the elemental mass-attenuation coefficients in the XCOM database . In fact, that is exactly how Hubbell and Seltzer calculated the mass-attenuation coefficients in the reference you give. The web interface to the XCOM database allows you to input the formula for a compound and a set of energies and then it outputs the mass-attenuation coefficients you want. See the link below.

http://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html

Thanks Jack, this is exactly what I need.  For some reason, I wasn't seeing the XCOM compound calculator in my earlier searches, only the tables for specific materials.

Thanks to both of you, as this link is very helpful for me.