By the time this "help" thread was posted, you probably already know what to do, but in case of someone having the same problem, I'm explaining it anyway (sorry for english mistakes anyway)

http://gamebanana.com/skins/download/136403
Once you download this, open the Space Bow folder and place the file with the bow you want to replace (either the normal huntsman, it's festive variant or the fortified compound) and place it on
steam\steamapps\common\Team Fortress 2\tf\custom folder (i don't really know how to explain that, so you better search a tutorial on google or youtube).