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 (23.51 USD): BGDigoo15%
(CouponsFromChina.com tip: apply code in your basket (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): vipupgrade8, f80018, TTxBG10, 2019SPEDM, BGYS417, AFfbG10, BGAFRP30, BGYS448, 502C6B, BGYS449, BGBGHFRI15, BGIEG149, BGBAPOHG, 0e7f33, BGDG15, BGdigoo15, FBCOUPON1, BGDGYS, 20%DG422
(probably won’t work, but you can try them out)
Price history and price alert
Do you need price history chart (for all/most countries) for Digoo DG-YS44 Sonic Toothbrush? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).