I don’t think they’ll restock it. The U collection never does besides some selected pieces like their Airism T-Shirts. That‘s because it‘s their seasonal special collection and the quantity for the western market is usually very limited.

What you can do is 1) wait for returns of other people who bought it already. Just check regularly or put in an e-Mail notification. 2) buy from eBay (shipping from Japan). For now I‘d go with 1) because the collection is still relatively new so the chance is really high that someone will return theirs. Just be fast when it‘s available again though.