The adapter came with a 528c, so it will definitely fit. All you need is a Torxdriver for the screws to attach it to your back. I can organize one for you if needed.
For feedback check my ebay account: fotolli
Paypal is fine if you add the fees and the price of 300€ is rather firm, but make me an offer if you feel that that´s too much.
And maybe do it via pm...