Aliexpress
Click here… to search for Xiaomi Mijia MJTXDDT01SKS Head Replacement on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Well, there is one coupon available right now.
Link: Banggood product page
Coupon (14.71 USD): BGHealth06
(CouponsFromChina.com tip: just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): HHHHHOT, 20%OFFSUMMER, ML15%Pro, vipupgrade8, BGSR15, 502C6B, BGDouble11HC, BGBFHC2, BGSHB7, BGXIAOMI811, BGXIAOMIE1, bgshOOp10, BGHome15%, bGhOnEy10, BGHOMEA15%, BgcLuBofErtA10, 13f142, BGAFF10OFF, BGCuponation10, BG10OFFAFF, BGwhielabel, BG10OFFAFF1, BANGGOODSD
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for Xiaomi Mijia MJTXDDT01SKS Head Replacement? There we go.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).