Direct power supply measurement range: DC 8-100V, Individual power supply range: DC 5-12V, Measurement range: DC 0-100V, Display format<10V, Acurancy: ±1%. Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
1. ($13.15): BG00c906
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGRCParts8, BGJUNEGSG9, Cuponation9, 9OFFSUMMER
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for Peacefair PZEM-023 0-100V Voltage Tester. The lowest price was: $10.91.
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)).