You can get KUULAA Mini Power Bank 4500mAh for $18.99 with coupon (from Banggood). Price history, coupons and price alert are available on this page. What is best price?
KUULAA KL-YD47 Mini 4500mAh Built-in Type-C Plug Emergency Power Bank External Battery Power Supply Fast Charging for iPhone 12 13 14 14Pro 14 Pro Max – Black+Type-C
Latest coupon and price update (UTC):
Banggood ($18.99)
Banggood warehouse is located in China. Hmmm… There is no active coupon in Banggood at this moment. But wait a sec… Is it a good price? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal $13.20)
Link: Banggood product page
Price: $18.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BG589b2e
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for KUULAA Mini Power Bank 4500mAh.
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)).