I'm lucky to have several Nikon Authorized repair facilities and dealers nearby. But even then some parts are hard to obtain. I've been waiting more than 3 weeks for a D800 battery door ordered through my repair shop. The owner of the repair shop offered to loan me the battery door from his D800.
The parts issue is just with Nikon USA. There are sources of parts outside the US at reasonable prices. For example, my battery door is available through E-Bay out of the UK at about the same price as a domestic replacement.