Because adapters are just metal rings filling the differences of the two mount (see Flange focal distance - Wikipedia, the free encyclopedia), lots of manufactures make them. There's no "model number".
All you need to know to search, is the mount type you want to adapt to NEX to.
In you case, basically a Nikon F mount to NEX adapter. I usually buy from rainbowimaging.biz, other people also had good experience with fotodiox. There're also Nikon to NEX adapters that allow you to control aperture, that usually mentions "for Nikon G lens". You don't need that. Just plain "Nikon F mount to NEX adapter" will do.
Sony NEX 5N * 2; Panasonic GH2/G3/GX1; Nikon D200/D600
SEL1855, Σ19+30; Adapted lenses in Canon FD, C/Y, Konica AR, m42, Minolta SR, Nikon F, & Tamron Adaptall mounts