Note that there is nothing for the D800 or D4, not even simple things like the 10 pin socket cover.
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From what I heard elsewhere the reverse. It was an old practice they discontinued, and so is actually a sign that they are not going to offer such support consistent with their sale-of-parts policy. This is legacy, not new (or so I have read).
At this point, all Nikon USA sold D800 and D4 cameras are under warranty, so all parts are free.
That being said, there are a myriad of cameras and lenses, with very simply replaced parts, which aren't for sale by Nikon to users.
This is not a definitive indication, to me, that Nikon is changing their policy regarding parts sales to users (pros and consumers) and 3rd party repair shops. I spoke with Nikon USA at the PDN Photo Expo and complained strongly to them about this policy, and some other repair (turn around time) and other problems and issues I've had recently. I didn't feel they were particularly receptive to considering change. I do know I wasn't the only one who spoke to them at the Expo about these issues, so maybe cumulatively we've made a difference. Time will tell.
If you think about Nikon's new part policy, the existing inventory or parts in non-authorized service personnel will dry up and since Nikon is not providing them to non-authorized service personnel one has to think about where they are coming form.
Many brands of electronics have a similar policy now. The test gear has gotten more specialized and they all have had problems with underqualified people attempting repairs which the end user ends up blaming the manufacturer. It this new policy by Nikon USA or world wide? If Nikon USA, there are two choices, buying from a local authorized service center or buying outside the country from shops that do not care about Nikon USA's policy. Stan St Petersburg Russia