000 times/min, Rated Voltage: 3.7 V, Waterproof Level: IPX7, Charger output: SV DC, Net Weight: 160 g, 1.5W, Rated Power: 1 W, Vibratiing frequency: 31, Model: ML-301, 500mA, Charging Mode: USB charging, Working time: 15 days per charge (2 minutes twice per day), Charger input: AC 110V-220V 50-60Hz, Package size: 85*60*196mm.
Just check coupons out (with price alert and history). Best price?
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 China. So I have checked for active coupons (all category coupons and old ones), but there was no working coupon in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGSPV12, BGDouble11HC, BGBFHC25, BGminleaf
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for Minleaf ML-301 Sonic Toothbrush is here. The lowest price was: $9.99.
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)).