Input Voltage: DC 5V, Net Weight: 136g, Brand: Usmile, Battery Capacity: 2500mAh, Modes: White/Clean/Soft, Handle Material: PA/ASA, Noise Standard: 60dB, Vibration Frequency: 38000/min, Waterproof: IPX7, Charging: Type-C 5H, Size: 30.5*30.5*252mm, Working Time: 180 Days, , Model: Y1S.
Just check coupons out (with price alert and history). 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 coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
1. ($64.39): BGCAPITALOS8
coupon code has to be applied in shop’s cart 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): BG421252, BG4ee866, BG641f34, BGUSEU02, BGHOM035, BG8ReviTrage, Cuponation9, BGc1dd31, BGf9f048, BG75597c, BG5e295c, BGde7078, BGbdfbb1, BGee7cef, BG589b2e, JanBGCoupon8, BGSaleFeb8, BGAUGUST8
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Usmile Y1S Sonic Toothbrush. The lowest price was: $29.62.
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)).