Hurray! I eventually got a bundle from here. Many thanks to Eric Le Lay for providing it.
This was after I failed to get the ‘running from source’ solution described on http://quodlibet.readthedocs.org/en/latest/downloads.html to work. Even after installing PyGObject with homebrew, I kept getting
ImportError: No module named gi.repository
. (And anaconda doesn’t even provide PyGObject.)