I have just checked coupons. The lowest price I could get is $35.99 for FNIRSI-FNB48P Ammeter Voltmeter USB Tester TYPE-C with BT (in Banggood). Price history, coupons and price alert are available on this page. Best price?
FNIRSI-FNB48P Ammeter Voltmeter USB Tester TYPE-C Fast Charge Detection Trigger Capacity Ripple Measurement with CNC Metal Shell – FNB48P With BT
Latest coupon and price update (UTC):
Banggood ($35.99)
Banggood warehouse is located in China. There are no coupons available at this moment in Banggood. The question is – is it a good price? Cool, average is $38.92, so current price is lower!
Link: Banggood product page
Price: $35.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGM1TOOLS88, BGddd805, BG20236Tool, BGTOOS729, BG814478, BG784871
(you can check these old coupons out, but these probably won’t work)
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
Do you need price history chart (for all/most countries) for FNIRSI-FNB48P Ammeter Voltmeter USB Tester TYPE-C with BT? There we go.
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)).