UPDATE: This is no longer necessary with Python3.4. It installs pip3 as part of the stock install.

I ended up posting this same question on the python mailing list, and got the following answer:

# download and install setuptools
curl -O https://bootstrap.pypa.io/ez_setup.py
python3 ez_setup.py
# download and install pip
curl -O https://bootstrap.pypa.io/get-pip.py
python3 get-pip.py

Which solved my question perfectly. After adding the following for my own:

cd /usr/local/bin
ln -s ../../../Library/Frameworks/Python.framework/Versions/3.3/bin/pip pip

So that I could run pip directly, I was able to:

# use pip to install
pip install pyserial


# Don't want it?
pip uninstall pyserial