If you want to use pip3 with your Anaconda Python 3 installation, you can copy pip.exe and pip-script.py in [Python 3]/Scripts/ to pip3.exe and pip3-script.py in the same folder. These will then show up in your PATH, so running pip3 install [x] will now work, and running pip install [x] will still work for your Python 2 installation.
It seems like you can do a similar thing with conda, if you are forced to install it for Spyder. Rename conda.exe, conda-env.exe, etc. and add [Python 2 Miniconda]/Scripts to your path.
(Thanks to Neil D. for the tip!)