Amazon.com: BoxWave Cable Compatible with Polar M400 (Cable by BoxWave) - Micro USB DuraCable, Braided Micro USB Charging Cable for Polar M400 - Space Grey : Electronics
USB cable for Polar RC3, A370, A360, M400 usb charging cord - 1m | eBay
For Polar M400, M450, A360, A370, V700 Sports Watch USB Data/Charger Cable - Walmart.com