Try
http://www.widgetwidget.com - they do a set of really nice icons which may include a Shuffle.
Also
http://www.iconfactory.com/preview.asp?type=search&id=231&query=iPod - the Smoothicons 11 set includes a shuffle icon.
To change the icon:
1. Select the icon file you want to use in the Finder.
2. Go to 'Show Info' in the Finder's File menu.
3. A window will appear. Select the icon in the top left hand corner. It will be highlighted in blue once you have done so, Press command-c. Or go to 'Copy' in the Finder's Edit menu.
4. Select the application/document/file whose icon you want to change.
5. Once more, select 'Show Info' from the File menu, or press command-i.
6. Click on the icon in the window that has just popped up.
7. Press command-v. You have just pasted in the icon that was on the clipboard.