Summary: You do not need a "crack" or unofficial site. Go to the Autodesk App Store, search for "Navisworks NWC Export Utility" for your specific year version, and download it for free using your Autodesk account.
If you cannot get the exporter to work (rare), you have two backup options: autodesk navisworks exporter full download
Autodesk provides this utility for free on their Apps (Exchange) website. You do not need a paid Navisworks license to use the exporter, but you generally need an Autodesk ID. Summary: You do not need a "crack" or unofficial site
Common exporters include: