You can get KWS-V20 USB Current Voltage Capacity Tester for $5.99 using coupon code (in Banggood). Just check coupons out (with price alert and history). You probably want to know what is the best price?
Current: 0-3A /, Time: 0-99H, Battery Capacity: 0-99999mAh, Voltage: 3V-9V /, Size: Approx. 7.2cmx 2.2cmx 1.1cm
Latest price update (UTC time):
Banggood ($5.99)
Banggood warehouse is located in China. There are no coupons available at this moment in Banggood. Is it cheap? Maybe there’re no more promotions for this item, because current price is higher than average (which is equal $4.99)
Link: Banggood product page
Price: $5.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGGines, BGTOOS729
(probably won’t work, but you can try them out)
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
Here is price history (for all/most countries) for KWS-V20 USB Current Voltage Capacity Tester.
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)).