Aliexpress
Click here… to search for Heng Long 3898-1 2.4G 1/16 US Sherman M4A3 RC Tank on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. Well, there is one coupon available right now.
Link: Banggood product page
Coupon (197.59 USD): CouponsDE
(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): BG173109, BGRC902, bGhOnEy10, BgoFErTaSchInA10, BG1725AS, BgcLuBofErtA10, 7bcdf9, BGAFF10OFF, BGCuponation10, BGDAVIS, BGHONEY2110, BGVehicle10, BGVehicles10
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Heng Long 3898-1 2.4G 1/16 US Sherman M4A3 RC Tank.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).