Where can I find haar cascades xml files?

Go to the opencv folder and check the data folder. You'll find haar-cascades for eyes, face, ears, upper body...:) And they do work properly.

Here's one site http://alereimondo.no-ip.org/OpenCV/34/ Don't know if they work though.

As the link in the previous answer seems to be dead, you can also try to download them from the OpenCV GitHub repository here