Aliexpress
Click here… to search for Airbot OMNIBUS F4 V6 RC Flight Controller on 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 (71.99 USD): 28RC
Coupon (89.99 USD): bGhOnEy10
Coupon (89.99 USD): BGdragonBoat
(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): F4V6, 502C6B, 15AB, TTxBG10, BGAIRB, 2019SPEDM, BGss9%rc, BGPAYPALSS, BGF4V6, AFfbG10, BGSS10%SW
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Check out price history chart (for all/most countries) for Airbot OMNIBUS F4 V6 RC Flight Controller.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).