Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. Coupons for Aluminum Alloy Whistle? Nope, there’re no coupons in Banggood.
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): f383d7, BGIPRee12, AFfbG10, 502C6B, BGBFCR21, BGCITYADS2019, BGVDay10%off, BGIPREEB, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGCAMP01, BgoFErTaSchInA10, BgcLuBofErtA10, BGZPBC15, BGTY704CP, BGHONEY2110, BG10OFFAFF, BGwhielabel, 13f142, BG10OFFAFF1, BG4d9120
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Aluminum Alloy Whistle.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).