Today in the grocery store I found a magazine called Nintendo Power Posters 2009. It had some nice Zelda posters, so I bought it. Looking at it later, I found there are two Phantasy Star Ø posters in it! It's a bit expensive at $9.99, but there are a lot of nice posters included.
So if your interested in having some PSØ posters (and in the US), look for this book in your local stores: Nintendo Power Posters. According to the cover, it'll be available until August 4.