I've taken a liking to Barnett cables. I run stock length, but they do make custom lengths also.
http://www.barnettclutches.com/
http://www.barnettclutches.com/service_center/service_center.aspx?cat_id=5
I like Barnett cables too - you can't order directly from Barnett anymore. Most bike shops can order them for you though.
Drag Specialties and J&P will have the extended wiring.
I would like to install ape hangers on my 2008 Harley Sportster XL1200R, however, I'm having a tough time finding extended throttle, idle, and clutch cables to fit this model bike. Has anyone done this on their Sportster? Where did you get the extended cables? Thanks!