Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (153.40 USD): BGMatt2022
(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): BGAT10, Parts8, 2019SPEDM, bgssaff9, parts8, BGaDmITAd, BGRC10, 502C6B, BGRDAT10, BGBFAFF2019, BGCITYADS2019, BGRDAT103, BGVDay10%off, BGAT102, BGTT10, bGhOnEy10, BGRDAT10CLE, BGSS10%SW, bgshOOp10, BGRC902, BGAT10OT, 7bcdf9, BGRCRR9, BGCuponation10, BGDAVIS, BGradio9, BG70e5fc, BGGAL8, BGRCParts8, Tabby20, BG1efeb0, 8Couponsde, MVC8SPRING, 8BGwbg2204, tRaDetRaCKeR, 8wEbgaInS5, pROMo8cuPoN, BG8RCToy, hoNEYbGdeAlS, BGJUNEGSG9, BGRCT10, BGRADIORU, BGToys8, JanBGCoupon8, BGSaleFeb8, BGSaleAD, BGMARCHSALE, BGToySale
(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 Radiolink AT10II RC Transmitter is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).