I am making Gabrielle Hamilton's braised dandelion greens, and need something mastica-like to give it that piney Greek flavor
If mastica has an anise-like flavor, you can use Pernod. Or maybe even Anisette or Sambuca, maybe? Or what about crushing up some juniper berries - they are also pine-y flavored.
Ouzo work too.
Ouzo will work too.