You can take a look at @alert's answer in this thread: Bootstrap Plone 3 with ancient bootstrap.py The problem was solved for an even older version (Python 2.4 and Python 3).
You basically download & install the old setuptools egg directly in the virtualenv. Then you use this virtualenv to buildout.
As a side note: Bringing those old Python/Plone versions to life is pretty painful. I did not succeed, when I was trying to compile OpenSSL 1.0 /w custom source hacks to make it work with an also compiled old Python version. I would not recommend wasting your time on this.