Don't the symbols in the various resource dictionaries in ESRI's Silverlight Symbol Gallery close enough for your needs, or do you need those exact symbols?
The ESRI Silverlight Viewer has several of these images in the \Images\Marker Symbols\ directory of the sites you create with their builder.
Couldn't you just write an app that saves all the marker symbols in a *.Style file to *.PNG files? How about just copying and pasting the individual symbols off that image you included here and save as individual PNG files? You'll probably want a better quality scan or whatever you used since those are a bit small and the second column is askew.