Aliexpress
Click here… to search for GDU O2 Drone 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 (716.66 USD): bGhOnEy10
Coupon (716.66 USD): BGSS10%SW
(CouponsFromChina.com tip: you should apply the coupon 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): dfa4c2, 502C6B, d8f2bb, TTxBG10, BGss9%rc, bgssaff9, AFfbG10, BGGDUO2, BGCITYADS2019, BGGDU24, BGGDUO2ES, BGVDay10%off
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for GDU O2 Drone is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).