If the art prints can be bought on the Japanese pokemon center sites you should be able to use these. If not, and they are exclusive to irl events these prints eventually pop up on ebay jp and even the NA ebay site.
I just read an article about this and the prints seem to only be available at the event campaign held in Japanese Pokemon Centers for 4,000 yen each. There are individuals who act like forwarding companies but I wouldn't go through them. You'll need to watch ebay or yahoo in the next few months and use one of the forwarding companies I gave you a link for.
If you have any other questions let me know! :) Hope I helped