You can create price alert here, copy coupons and view price history. Do you want to know what the best price is?
Output current: 500mAh / 1000mAh, Standby current: No more than 15mAh, Output voltage: 1000mAh and output voltage is 4.75 – 5.25V
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. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($16.27): 00c906
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Old coupons (from the oldest to the newest): AC18, MLKT1, ac18, AC19, BGAFF10OFF, BGCuponation10, 4BLF, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BANGGOODSD, 6GSGIT, BGTorch4
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for LiitoKala Lii-S1 Battery Charger? There we go.
Price records source(s): Gearbest, 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)).