4W 5V Solar Panel Charger Micro USB (Banggood, Aliexpress: Weight After Packaging 295G (Subject To The Actual Product), Wire Length About 3M, Plate Weight About 193G (Subject To The Actual Product), Size 175 * 115 * 10Mm, Material Grade A Monocrystalline Silicon Solar Panel, Short Circuit Voltage 6.2V, Package Size 200 * 128 * 73Mm (White High-Grade Neutral Box), Working Voltage 5V (Charging 3V-5V Battery), Short Circuit Current 750Ma, Interface Micro USB (Android), Power 4W, Working Current 0-800Ma (the best price with coupon)).
Just check coupons out (with price alert and history). What is the best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
1. ($22.49): BGAMMT03
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGa46747, BGCarEle4, BGissam740, BGSCM11, BGCarEle5, BGLMQ15
(these coupons are old, so probably won’t work)
Price history and price alert
Do you need price history chart (for all/most countries) for 4W 5V Solar Panel Charger Micro USB? There we go. The lowest price was: $12.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).