I have just checked coupons. The lowest price I could get is 21.69 USD for Portable Solar Panel Kit (in Banggood). Price history, coupons and price alert are available on this page. What is best price?
Latest price update (UTC time):
Banggood (21.69 USD)
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood. What about the price? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal 20.63 USD)
Link: Banggood product page
Price: 21.69 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BG589b2e, BGd2f208, BGET12, BGET10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Aliexpress
Click here… to search for 13W Portable Solar Panel Kit 5V on Aliexpress
Here are coupons that you can use.
Price history and price alert
Do you need price history chart (for all/most countries) for 13W Portable Solar Panel Kit 5V? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).