Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
Coupon (27.93 USD): 13f142
(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): 2be6e9, 935bc1, plxmnl, 0e7f33, FBCOUPON1, BGAFF10OFF, BGCuponation10
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for Xiaomi FH100 Headlamp is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).