Sprites with shadows have uneven edges

I would like my sprites to cast shadows, but there is no shader that can render both shadows AND nice edges. Some shaders can render shadows (mobile/bumped diffuse - righ ball), but sprites have uneven edges, while others can render nice edges (sprites/default - left ball), but cast no shadow.

Is there any shader that supports both, or is there any fix? Thank you for any ideas.

Have you tried to use static shadows (Secondary Sprites animated to match with the Primary ones)? or your game must have realtime shadows?