How can I search for an in-model component (on Mac)?

This can’t be done in the Component Window. The Outliner, which has a search box for internal components and groups is indeed the way to do it. If you have a great number of Components it is best to have a strict naming-convention to organize your model (EXT_CONS_COLUM_name) and also in your Layers.
Other workarounds:
-You could upload all your Components in your 3D warehouse and use tags for searching purposes, so they would show up in MyModels or MyCollections in the Component Window.