I use this GroovyNoodle Silicone Jacketed Wire 7.5M - 8 pack - Solarbotics Ltd.
It's multistranded so doesn't play well with a breadboard.
Adafruit would be the best place to look. They have more wearables than other suppliers. I would believe that wires in wearables would be flexible.
I'd suggest taking a trip to your local hardware store and seeing what they have.