Check coupons or create price alert down below. What is the best price?
Quiescent current 10uA (max), Working voltage 3.7V, Input power 1.25W (max), Maximum working current 130mA (max), Ambient temperature – 10 ℃ – 50 ℃, Battery capacity 250mah, Charging voltage 5V / 1A, Charging current 250mA (max), Continuous working time (maximum gear) About 2.5h, Maximum output power 0.75w (max), Charging Way USB Charging, Low power warning About 2.5h, Low power off < 3.2V, Charging time About 2H, Material ABS, Charging interface DC charging, Power supply mode Buried polymer battery, Waterproof IPX6
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
1. ($28.22): 00c906
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGBTJU50, BGHU0275, BGBTJUT6, BGFE25ZXY, BGAFF10OFF, BGPFHC01, BGMASE01, BGORALIRRI2, BGitIPX6, BGMA2904, BGAP2713, BGGREE1002, BGMAR2406, BGwhielabel, 13f142, BG10OFFAFF1, BGSEXP152, BGHealth06
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Electric Dental Calculus Remover.
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)).