Hi Mike,

The only way that I know is to attend the following Oracle course:
http://education.oracle.com/pls/web_...S&source_call=
This is the only one applicable source.
There is no published book about the subject as you've already found.
Another my suggestion (but not approved from Oracle and requiring more research) is to find two sources (book or student guide): "Oracle9i: New Features for Administrators" and "Oracle 10g: New Features for Administrators" and to bring them together, to learn both of them and to go for the exam. As you can see, there is no Practise Test on the site of http://www.selftestsoftware.com about this exam as well.
Keep in mind that you will become an OCP DBA in Oracle 10g but you will not be recognized as an OCP DBA in Oracle9i, you will just jump over this credential - Oracle will say: yes, you are OCP 10g but you are not OCP 9i.
If I am wrong about this, please let someone correct me.