Scodanibbio Sheet Music

His music was available from his website. Try sending a message and see if anyone is selling his music. In answer to your second question, I would imagine that everything you need to play the piece will be on the page.

 

In regards to notation, if you have a good comprehensive music library around you (probably at a college) that library may have a copy of Bertram Turetzky's "Contemporary Contrabass" which is one of the most comprehensive studies on extended techniques for double bass. Unfortunately though, it is really hard to find nowadays.
The Modern Double Bass
This website is a great resource on extended techniques and has a lot of great explanation on how to execute the techniques and how to notate them. If I remember right, Ashley is a TB user so maybe he'll chime in on this thread!

 

I believe you can still contact his wife via the website. She sells the scores herself.

The scores are all handwritten, but mostly very clear with some instructions. You'll probably want a lesson or two with somebody who knows the techniques.

You might be disappointed to learn the 6th study, Farewell, is an improvisation. The score isn't very helpful for that one.

 

Yeah, his wife was very prompt in getting back to me when I ordered some music from her. The 3 scores I ordered all look great.