Try a clock parts supply company for ladder chain:

  TimeSavers, Box 12700, Scottsdale AZ 85267.
  tel: 602-483-3711 (Product Information).

Their catalogue lists No 10807 1.37 MM, 34 links per foot; 6 feet is
around $15 plus postage.  Orders less than $15 carry $3 extra charge.
I believe ladder chain comes from Europe.  Perhaps they can order it.

Anyway, it is possible to mend old chain and make new chain.  The Black
Forest clock makers made it by hand and in later years by machine.

Werner Grunbaum

 [ 34 links per foot is 9 mm pitch; 1.37 mm (.053 inch) must be the
 [ wire diameter.  That's big!   -- Robbie