I drew them myself. This is how I did it
1. I made the shadows on the upper and lower floors
2. I made a grid the width of each step, with a height of (pixels between upper and lower shadows) / (number of steps)
3. I used the path tool with polygonal and snap to grid enabled to save a path of what I wanted removed/added
4. I used the path flipped or rotated to cut or add shadows to the steps
Here is a screen grab of the steps with the grid on and the path selected:
This one I used to cut the lower shadow off the stairs, I then flipped it, offset it slightly and filled it with the black of the shadows.
I did the same thing on the vertical stairs, but I also added a 2nd path for the individual steps
I am also part way through writing a script that adds the shadows using motion blur instead of using "drop shadows" its not quite ready yet though as I cant get it to blur correctly.
Standard drop shadow is on the left, my script creates the shadow on the right(with options for distance, opacity, blur etc).