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

EPEL provides only Python 2.6

Answer: 
Have you checked any of these repos:

* [Dag Wieers](http://dag.wieers.com/rpm/)
* [Dries](http://dries.ulyssis.org/rpm/)
* [rpmforge](http://rpmrepo.org/RPMforge)
* [livna](http://rpm.livna.org/)

Is it ok if you have the rpm instead of a repo (i.e. can you take care of dependencies if it arises?). If so, try [phone](http://rpm.pbone.net) or [rpmfind](http://rpmfind.net). If none of the above helps, consider building from source tar balls. By far that will be the easiest.
You can try my build adapted from Fedora 16:
<http://ftp.srce.hr/redhat/test/el5/x86_64/>