If you're talking about this case (http://www.sony.jp/walkman/products/CKL-NWZ1000/) - it's the leather one. I have it. If you never take it out to stand it up, the build quality will be fine. Or are you talking about another one? And I would say outside of Japan, your only option will most likely be Sony cases. The only annoying part of that case is you need to open it every time you want to change albums, etc. So if you fiddle with your Walkman more often than not, it may not be the right case. Although you can ditch the leather/flip part and just use the plastic bit as the case, too.
I have two line out cables for my WM-Port - this one (http://www.amazon.com/gp/product/B003UCI2CI/ref=oh_o05_s00_i00_details) and I just picked up the longer version of it while in Japan.