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 (15.93 USD): BGGAL8
Coupon (15.93 USD): BGRCParts8
(CouponsFromChina.com tip: just apply this code in your 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): FS2A, 20OFFRSF, Parts8, BGaDmITAd, BGCITYADS2019, 2020CNY, BGVDay10%off, BGFS12, BGFKY11, bGhOnEy10, BGTT10, BGflysky11, BGRCRR9, BG11SHOP, 13f142, BGCuponation10, BGDAVIS, BG70e5fc
(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 FS2A 4CH AFHDS 2A Receiver.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).