Aliexpress
Click here… to search for 30.5×30.5mm Racerstar AirF7 Lite 3-6S Flight Controller on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (25.19 USD): BGHONEY2110
Coupon (25.75 USD): BGDAVIS
(CouponsFromChina.com tip: apply it 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): BGTT10, BGF7LITE, BGHALLOWEEN, BgcLuBofErtA10, BGRSLITE, BG11Racer, BG15LITE, BGTHAIRF7, BGF7RSBF, BGBFF7LITE, BGAFF10OFF, BGCuponation10
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for 30.5×30.5mm Racerstar AirF7 Lite 3-6S Flight Controller.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).