I been using Ken Oconnor Racing here locally in CT for all my bike cranks and he has done a few. Crazy anal about details and good pricing. He's done a bunch of vintage bike cranks for me that are a PITA to get true and he is never happy unless they are less than .001" inline.
http://www.kenoconnorracing.com/
I was always told that you could only balance the crank if you sent the piston, pin, bearing with it as you need the whole assembly to get it right.