Isopix has posted an additional 15 thumbnails of Keanu and his lady friend and x17online has the whole series of 20 photos. Close ups leave no doubt that she is in fact Bojana Novakovic. The caption with the photos indicates they were riding on Mulholland Dr. and while they are dated August 4 based on their clothes they appear to be from the Saturday outing.
Update: The main post has been updated to include the x17online link for the photos. The story link is here.