I build my own cables, and have done some nice 3.5mm - RCA which are very flexible. Using Toxic Cables pure silver cable it is flexible and sounds great!
Make your own cables, not difficult and very flexible if you leave it bare:
Obviously copper is cheaper and still sounds great.
But even the silver (2ft) is only about £50 in materials (without snazzy y-split like above)
Toxic cables do have some cheaper silver cable now too, so only about £35 in materials.