Battery Life 30d after fully charged, Color White, Brushing Mode ①Standard Mode, Waterproof Rating IPX7, Size L187.5mm, Rated Voltage 3.7V, Net Weight 41.7g, Rated Power 0.6W, Noise <60db, Model MES603, Charging Way USB Charging, Φ28.5mm, ②Gentle Mode, Charging Time <4 hours. Basically copy coupon, view price history or create e-mail price alert. 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.
Link: Banggood product page
1. ($26.99): BGHONEY2110
2. ($28.99): 13f142
apply code in your basket (cart) after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BG3T100, BGGR297, BGHU460, BG3T100v19, 502C6B, BG2SBR, BGDouble11HC, BG3P56, BG4Men2, BGMi3P, BGOMG23, BG3MiJ2, BG2MFC, BGTMCB7, bgshOOp10, bGhOnEy10, BGE3811, BGHB20, BGSD58965, BgcLuBofErtA10, BGNMJI1200, BGNNHN0101, BGAFF10OFF, BGCuponation10
(I don’t think these’re gonna work, but you can try ’em out anyway)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – 3Pcs Xiaomi Mijia T100 Sonic Toothbrush [EU] ($-3)
Price history and price alert
Check out price history chart (for all/most countries) for 3Pcs Xiaomi Mijia T100 Sonic Toothbrush. The lowest price was: $17.99.
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)).