Sprite-Renderer casting & receiving 3D shadows

The standard sprite renderer does not cast or receive 3D shadows by default. It's deactivated.

According to my research this is only a matter of settings inside the renderer. However, the renderer can't be changed.

How is it possible to get a copy of the SpriteRenderer, that I can modify it's code and put in my personal assets folder for further use?

Or is there another solution to this? Any ideas might help.