Aliexpress
Click here… to search for 2x Oclean SE/One Toothbrush Heads Warm White on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (8.99 USD): BGHONEY2110
Coupon (8.99 USD): BG10OFFAFF
(CouponsFromChina.com tip: put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): ML15%Pro, vipupgrade8, BGOCTBR, BGMIB2, 502C6B, bGhOnEy10, BGHB20, BgoFErTaSchInA10, BGSD58965, BgcLuBofErtA10, BGHBHJ107, BGAFF10OFF
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for 2x Oclean SE/One Toothbrush Heads Warm White.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).