Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Europe 
. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood. I don’t really know if this price is reasonable, coz there’s no price history in my DB.
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
There were country-specific coupon codes published on Couponsfromchina social channels and price alerts. Coupon price may vary by country, because there’re different VAT rates, shipping cost etc. There is a chance that some latest coupons are still working:
Price history and price alert
It doesn’t make sense to generate price history chart, because there is one price record which is: 39.99 USD.
You can set price alert (for Banggood).