I've never heard of such a conversion tool, and if it exists, I want one!
I'm guessing you probably will not see one because Lotus databases are radically different from MS Office's collective programs. Lotus Smart Suite was closer to Office. It is easier to import from Office into a Notes database than to export the entire NSF to Office.
However, if you can get a working copy of Notes, then you should be able to export the data from any view in an opened .NSF file. To do that just select the view, then the data (EDIT-SELECT ALL), then export it (FILE--EXPORT). Save it as either Tabular Text or Structured Text, then import that into Excel.