I can't believe I'm going to mention the company that canned my Dad the week before his 50th birthday... But he survived and thrived, so here goes.
Check Flowserve - if they can't do it, they should be in the right industry to know who can.
http://www.flowserve.com/
What if you redefine your need (a little)?
Could you use a flexible channel cable tray/trough similar to what's used in elevators and computer printer heads (sort of)?
I'm picturing a fixed-length cable in a segmented, flexible carrier that moves along a linear range of positions.
What if the wind was blowing strongly, and one or more OH line segments were too long, too slack, too close, etc. where phases could "slap" together ? If the wind direction were mostly parallel to the conductors, it's less likely to blow phases together.
You might be able to see burned...
This doesn't sound like a major problem.
If there's a special mechanical strength need try someone like optical fiber corp ( occfiber.com ); they make tactical cables for the military.
