Aliexpress
Here are coupons that you can use.
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. China – Digoo DG-BC20 Bathroom Thermometer Hygrometer Black (-3 USD)
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (3.88 USD): BGBS2038
Coupon (3.99 USD): BGBC203
Coupon (5.61 USD): AFfbG10
Coupon (5.61 USD): BGBFAFF2019
(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): BC2018, BC333, 484ac6, 502C6B, 0404digoo, e2bcea, vipupgrade8, TTxBG10, BGDigoo15%, BGBC2033, BGBC2039, BGCITYADS2019, BGBFI388, BGBGHFRI15, BGROG215, BG20bc3, BGVDay10%off, BGDG15, bGhOnEy10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. China – Digoo DG-BC20 Bathroom Thermometer Hygrometer Black (-3 USD)
Price history and price alert
Price history (for all/most countries) for Digoo DG-BC20 IP45 Thermometer Hygrometer White is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).