Hello, I am the person that owns the Dreamy Theater Controller you saw at Metrocon.
When the controller was announced last year, I checked my usual import sites to see if they would allow for preorders for this. Luckily, Play-Asia started to put them up for $374 and $80 shipping. I put a preorder AS SOON AS I COULD. There was only the initial run sold, and no more were made. I am lucy to own it for $450. Now, you could hope that they make a controller for Project Diva f PS3, but that may or may not come.
Since you are passionate about this, I'll help you out a little: page12.auctions.yahoo.co.jp/jp/auction/p291406962
A controller is being sold right now on Yahoo Japan Auctions. A service that I use is Shopping Mall Japan (SMJ). They act as a middleman service for Yahoo Japan Auctions (YJA) and Japanese online stores. If you want to bid on products on YJA, they will deal with getting the item from the seller and ship it to you. Keep in mind that you need quite a bit of money, as you must pay for the product's final bid price, a commision price to SMJ based on a percentage of the final bid price, shipping from the seller to their warehouses, and shipping from their warehouses to you. You must also give SMJ a bidding deposit to aloow you to bid up to 5 times the amount on YJA (e.g. you give them a $100 deposit to allow bidding on YJA up to $500). I would suggest getting around $700 if you attempt to do this.
Even if you decide not to get it right and hope for another one to show up later, just use the text from here: 初音ミク ドリーミーシアター 2nd 専用コントローラー , paste it on YJA's search to find it in the future.
Hope this helps you.