Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (660.99 USD): 7bcdf9
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGdy02, PICODICOM, bGpAnDacHeCk
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for F-wheel DYU D3 10.4Ah Electric Bike Black.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).