When I bought my N9, I got one in a beat-up housing with the intention of swapping the outers. I bought a housing through eBay from China, shipped to the UK for ~£10, similar to this one. The item included all the electronic components that are part of the case, so was a straight swap, and was a very good match for the original.

The housing I was sent happened to have one of the four screwholes mis-moulded, but on sending a picture to the seller they offered to send another at no charge (and didn't need the other returned). I never actually got around to swapping to the replacement: it's sat in the cupboard as a spare.

Re: wear and tear, I have a snap-on case over the housing, but the exposed portions have shown little wear in the year I've owned my N9.