Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (159.16 USD): BGTT10
Coupon (159.16 USD): bGhOnEy10
Coupon (162.69 USD): Parts8
(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): 502C6B, 8b498c, TTxBG10, BGObserver, BGBCFPV, BGAIRP12, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, BGOTC21
(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 Zeta Sky Observer Sky Lark RC Airplane Kit.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).