Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (508.99 USD): 13f142
(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): BG692973, aff7off, BGbfae7c, bgchinafest, 7bcdf9, Email5, bgshOOp10, 7d18f7
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Huawei M6 CN 4/128GB WIFI Tablet Gray is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).