You can get Charging Cable for for 13.41 USD with coupon (from Banggood). You can create price alert here, copy coupons and view price history. What is the best price?
Latest coupon and price update (UTC):
Banggood (13.41 USD)
Banggood warehouse is located in China. Too bad there’s no coupon right now in Banggood. Is it cheap? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal 2.14 USD)
Link: Banggood product page
Price: 13.41 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGM4CHARGE, AFfbG10, BGVDay10%off, bgwba, BGAFF10OFF, BGSS10%SW, BGdragonBoat, BgoFErTaSchInA10, BgcLuBofErtA10, BGHONEY2110, 13f142, BANGGOODSD, 6GSGIT, BG51f436, BG00c906, ADMITAD2212, 2022ACTIESNL, Terence, Tabby20, 2203ActiesNL, BG1efeb0, MVC8SPRING, 8BGwbg2204, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BGJUNEGSG9, TTSUMMER8, Cuponation9, BG589b2e
(these coupons are old, so probably won’t work)
Aliexpress
Here are coupons that you can use.
Price history and price alert
Do you need price history chart (for all/most countries) for 25cm Charging Cable for Mi Band 4? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).