Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. You can get coupon down below.
Link: Banggood product page
Coupon (39.99 USD): BG16261c
(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): 8wEbgaInS5, pROMo8cuPoN, BG8RCToy, hoNEYbGdeAlS, BGToys1, BGRCT10, BGJUNEGSG9, COUPONSDE1wk, Cuponation9, BGMatt2022, BGToys8, BGGutscheine, BG8OFFCOUPON, TTBLACK5, BGSaleFeb8, BGSaleAD, BGMARCHSALE
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for 25.5×25.5mm JHEMCU GSF405A F4 AIO Flight Controller 5V BEC 1-2S is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).