How about Resurf3d?

someone mentioned it already in an earlier thread:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4013.5


Mesh to single NURBS

http://www.resurf3d.com/mesh2snurbs.htm


and with a price tag of "only" $119, it surprisingly produces some reasonable results.

best wishes,
marco