Amazon has Keten NES Classic Controller Extension Cable USB Cord 6ft 1.8M for Nintendo NES Classic Edition 2-Pack $2.36 after code.
https://www.amazon.com/dp/B01NBEA0ZO?th=1
Save 21% each on Qualifying items offered by Keten Direct when you purchase 1 or more. Enter code X9REC3WB at checkout