Jython ships with pip and it is still possible to create virtualenvs by using older versions of tools:
sudo {port|brew|apt|dnf} install jython
sudo jython -m pip install virtualenv==15.2.0
jython -m virtualenv --no-pip --no-wheel .jenv
.jenv/bin/easy_install pip==19.1.1
.jenv/bin/pip install -U setuptools==44.1.1