For those who were waiting, the chapter is now available at CLAMP No Lumiere!
The subbed version of XXXHOLiC Shunmuki Part 1 has finally been released by ACG fansub (MKV format).
You can download the torrent here.
UPDATE: Here‘s another option by SubsFuckingWhere fansub.
These are also available in direct download here.
Thanks to everyone who let me know about this (Seishirou-san and Elias-san)!