Answer to: Where can I buy a custom back housing for my phone?I have switched out back cases for iPhones three times now, whilst I can say they're not always reliable, I do agree with Dan in that they sometimes have some antenna defects. But in answer to your question a simple eBay search will find you your backdoor/housing part, probably from China where they're all made. They look amazing though :D
Answer to: My iPhone 5 home button spinsThere's meant to be a rubber gasket surrounding the home button on the underside of the screen which is meant to stop looseness and spinning. Was your phone recently repaired? If so, my guess is that it was left out or damaged, thankfully it is just a cheap piece of rubber which can be bought for a dollar if need be.