Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
Coupon (55.99 USD): 13f142
(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): BGXP631, bgshOOp10, bGhOnEy10, BGHome15%, BGHOMEA15%, BgcLuBofErtA10, BGAFF10OFF, BGCuponation10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for VIOMI Pro 2 In 1 Electric Water Heating Bottle 300W is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).