Question: Are there any half-official repositories for CentOS 5 with Python 2.7?

EPEL provides only Python 2.6

Answer: 
You can try to get 2.6 srpm from epel you've found, extract spec file from it, change version number and rebuild it.

However, be carefull: there are a lot of packages depending on python 2.4 on el5 (like yum). You'll probably need to ensure that you are installing 2.4 and 2.7 at the same time or that you've rebuild everything depending on 2.4.
Not that I am aware of at this time, but then again it would be prudent to learn a standard gunzip make install instead of relying on package managers.