I'm looking for a "clean" one too, can't find them. Bump for a find.
EDIT: I've managed to find a couple but the logo is the new one based off Man Of Steel that is coming out soon. I found the last one to be the best to use because when in horizontal flip, the edges slowly fades out perfectly.
<img src="http://www.ipadforums.net/attachment.php?attachmentid=36783"/>
<img src="http://www.ipadforums.net/attachment.php?attachmentid=36784"/>
<img src="http://www.ipadforums.net/attachment.php?attachmentid=36785"/>