Don Teach posted,

  "Ronsen will weight match to your samples.  Erwin's Piano Restoration
  in Modesto, California, also sells a version of this hammer and can
  bore them plus mount them on shanks ready to install.  PianoTek also
  has this service."

I did not know that Dale (Erwin's Piano Restoration) offered this
service; he has a great crew there (includes his wife) and is very
detail-oriented.  I would trust his work.  See

  http://www.erwinspiano.com/about-us/ 

His shop is in his backyard and is very well equipped (I'm jealous!).
Since I actually met and know the guy, I thought I'd post my experience
and opinion, for what it's worth!  (Yeah, free advice... <smile>)

David Dewey