Looking for a special piece of starfy merchandise

I see what you mean. These are one of those items that are uncommon even on Japanese auction sites.

Your best bet is to use a Japanese proxy service (a service where someone will bid on a Japanese auction site for you). The one I use is called Japonica Market and the staff are reliable and quite friendly), and to keep looking for it on Yahoo Auctions Japan until it appears. You never know with those what will be available, as I recently saw a listing for the Tomy big Starfy plush toy there which is really rare. The best keyword to search for is "スタフィー" (Japanese for Starfy).

Hope this helps!