Ladder chain isn't readily available, but there are a few people who
can make it up for you.  Since each job requires the fabrication of a
special jig to bend the loops, be prepared for the price tag involved.

One such individual who does this type of work is a clockmaker and organ
rebuilter, Jim Moss, of Cambridge, Mass.  He can be contacted via email
at <clkmkr@tiac.net>.

You might also consider going to the extent of making up such a jig
yourself.  Granted, it might only be used once, but it will be far
cheaper than having someone make up the length you need, by the hour
rate.

Ern Grover
Father & Son Clockworks
http://www.cybertours.com/~ern