Silicone-sheathing wire is super-flexible and soft, and its also strong! Able to handle up to 200°C and up to 600V, it will do when PVC covered wire
Silicone Cover Stranded-Core Wire - 2m 30AWG Green : ID 2005 : $0.75 : Adafruit Industries, Unique & fun DIY electronics and kits
Silicone Wire 30AWG 30 Gauge Flexible Tinned Copper Standard High-Temperature Hookup Wire Grey 75m/246ft
White Stringing Round Elastic Cord for BJD Doll 1mm 1.5mm 2mm 2.5mm 3mm 3.5mm 4mm - Israel
adafruit-Silicone Cover Stranded-Core Wire - 50ft 30AWG Yellow ADA3167
Products Tagged Silicone Wiring - Elmwood Electronics
Adafruit Industries Pi GRRL Zero - Zero and Case Not Included - Micro Center
Prototyping Supplies