My table saw came with a riving knife to which the crown guard attaches. It works very well but is limiting for certain jobs as you can only make a full depth cut as the knife sits much higher than the blade.
There is no other option from the manufacturer so I decided to make myself a new riving knife. Picture below demonstrate the process, any questions please ask.
To make the knife I used my portable bandsaw with it's table attachment (pics here on another thread), and files to refine the shape. Not a long process and it works perfectly.