Here are two torrents (probably the same file though) to download the OAD of XXXHOLiC Shunmuki Part 2:
Pick only one of the two sources, no need to download both =)
Update: Direct download link: http://www.megaupload.com/?d=55SWGC55
Update 2: cardcaptorkiki has scans of XXXHOLiC #15 (including the cover, box, dvd, etc.) in here.