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 (37.43 USD): BGAFF10OFF
Coupon (37.43 USD): bGhOnEy10
(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): AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, BGN252M, BGMPB2020
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Tenda AC8 Gigabit Dual-band Router is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).