Aliexpress
Click here… to search for Universal Toothbrush Travel Box for Xiaomi/MIjia/Soocas/Oclean/Dr.bei on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (10.73 USD): 2022ACTIESNL
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply 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): BGTB01, BGTOOTHBOX, AFfbG10, BGBOX19D, BGEOJ19, 502C6B, BGVOE19, BCBOX188, BGMIBOX88, BGXYBO178, BGBOXALL32, BGTB177, BGBFAFF2019, BGBOYX177, BGCITYADS2019, BGBFI69, BGJHG199, BGOFB897, BGORTN94, BGOERG25, BGBAPOHG, BGIGN169, BGHNUJ4, BGVDay10%off, BGHNO18, BG0303CYY, BG303cv, BGAFF10OFF, BGTT10, BG19BOXW, bGhOnEy10, BGdragonBoat, BGCNETTB, BGHome15%, BgcLuBofErtA10, BGHONEY2110, BG10OFFAFF, BGwhielabel, 13f142, BG10OFFAFF1, BANGGOODSD, BGHealth06, 00c906
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for Universal Toothbrush Travel Box for Xiaomi/MIjia/Soocas/Oclean/Dr.bei.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).