Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (76.71 USD): Cuponation9
Coupon (79.24 USD): BG00c906
(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): BGDNQ06HET, BGHOMEA13, BGCuponation10, 13f142, BG10OFFAFF1, 6GSGIT, 00c906, ADMITAD2212, 2022ACTIESNL, Terence, Tabby20, 2203ActiesNL, BG1efeb0, 8Couponsde, MVC8SPRING, pROMo8cuPoN, hoNEYbGdeAlS, BGJUNEGSG9, DealBGimpact, 9OFFSUMMER, BGAHPU13
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Deerma DEM-DNQ06 Electric Heater is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).