There is no such library available as bone data is extracted by CT SCAN and it vary patient to patient. But you may find some general CAD file on grabcad in any of cad supported file.

I was thinking of the CT and MRI scans that are available for research use, mainly cancer research to my knowledge. Some other work may have already extracted the files and made CAD files you could use. There was a similar answer already posted that might help you get scans.

https://www.researchgate.net/post/Can_anyone_suggest_me_any_website_for_downloading_DICOM_files

Hope this helps.

Oscar