Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mijia Floor Fan DC Frequency Cable.
Price records source(s): Gearbest
Click on image to enlarge. 
You can set price alert (for Banggood).
This is the version without a built-in battery!
Text is wrong.
No:
– Built-in 2800mAh Li-ion battery,
– Working time: 500h (1.8W lowest power).
Thanks!