For such things I believe eBay is unbeatable, but you’ll need some patience, at the moment I can’t see any german topcase for sale. You can find just the keyboard, from China/Hong-Kong but the price is very steep, around 140/150€ and you have to do the job or pay someone for that. If you can wait, I’m quite confident you’ll find one, parts are very expensive for such Macbook and one day or the other someone will crash the screen and decide it’s not worth replacing it and sell the Macbook for parts :)