Found the Japanese sites that I believe say the clear files I have were merchandise exclusively made for the art exhibitions (obviously in Japanese, so not 100% sure)
http://www.excite.co.jp/News/game/20...yer_22560.html
http://p2.pixiv.net/2011/07/28/24046.html
The following link is a random blog (I think it's a blog?) of someone in Japan who went to the Art Exhibit. I only post it because they have a scan of one of my clear files
http://blogs.yahoo.co.jp/starwars0906/6725006.html
Also someone commented about how good it looked
Another website I found had something translate to: "These goods are sold exclusively at the venue(referring to the art exhibition)"
So I would assume it was the only way to get them
I guess that would put these into a convention type bonus item? Similar to something you could only get at Pax, or comicon etc.
Not super rare, but still hard to find