Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (115.11 USD): BgGoodie9
Coupon (115.11 USD): Cuponation9
Coupon (116.37 USD): BG8ReviTrage
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply 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): 2203ActiesNL, hoNEYbGdeAlS, BGJUNEGSG9, 9OFFSUMMER
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for PowMr MPPT 60A 12V 24V 36V 48V Solar Charger Controller.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).