Just check coupons out (with price alert and history). Best price?
Dust and water splash: IP54, Powered by 2x 1.5V LR6 AAA batteries (not included), High accuracy and wide measuring range up to 40m
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
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Price history and price alert
There is only one database record (it was for $14.8), so you can’t see price history chart.
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)).