I just discovered that Patch 1.03 was available on GOG, so I downloaded it and ran the package file (I'm on a Mac, and the Patch fileneme was patch_pillars_of_eternity_2.1.0.pkg). It seemed to go through the process but then existed with a message saying "This patch will not work with your game version!".
Any idea what the problem is? When I start the game, the version number in the bottom left hand corner is v1.0.2.0508.