Aliexpress
Click here… to search for Xiaomi ZMI QINGHE Mosquito Dispeller on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (21.47 USD): Terence
Coupon (21.70 USD): BG00c906
(CouponsFromChina.com tip: this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): TTxBG10, BGzmiqin, bgssaff9, AFfbG10, BGZMI139, BGBFAFF2019, BGCITYADS2019, BGBGHFRI15, 13f142, BGVDay10%off, BGHOMEG12, BGAFF10OFF, bGhOnEy10, BGdragonBoat, bgshOOp10, BGHome15%, BGTT10, BGAFF7OFF, BGCuponation10, BGHONEY2110, BGAP2003, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BANGGOODSD, 6GSGIT, BGBF20off2, 00c906, BGAlerabat1
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi ZMI QINGHE Mosquito Dispeller.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).