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 (25.29 USD): BG38928b
Coupon (28.51 USD): BG518648
Coupon (32.19 USD): BG867610
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Price history and price alert
Price history (for all/most countries) for 4DRC 999-614 2.4G 4WD RC Water Ball Tank is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).