Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Hmmm… There is no active coupon in Banggood at this moment.
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
Old coupons (from the oldest to the newest): BG22ead4, BG589b2e, BGET12, BG3f3dbf, BGET10
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for MOHOO 30A 12V/24V 5V 3A Dual USB Solar Charge Controller.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).