Nikon makes the ML-3 IR release. It's rather pricey.
Any 10 pin socket compatible release will work. If it's listed for other 10 pin socket cameras, it will work on the D800.
There are a lot for sale on eBay. B&H and other online stores list a few choices too. I got a Promaster brand RF release at my local camera store; I'm happy with it.
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