Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
Coupon (33.99 USD): BGHBHJ105
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): BGDigoo15%, 40645d, 20%DG422, BGDGASG, bGhOnEy10, BGHB20, BgoFErTaSchInA10, BGSD58965, BgcLuBofErtA10
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for DIGOO Nicefeel DG-FC152 Water Flosser.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).