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 (18.99 USD): BGHAIRDRYER
Coupon (29.73 USD): bGhOnEy10
Coupon (29.73 USD): BGHOMEA15%
Coupon (29.73 USD): BgcLuBofErtA10
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart 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): 033b38, 502C6B, vipupgrade8, TTxBG10, aff7off, bgssaff9, AFfbG10, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, BGHOMEG12, FBCOUPON1, BGdragonBoat, BGSS10%SW, bgshOOp10, BGHome15%
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi Reepro RP-HC04 Hair Dryer is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).