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 (269.99 USD): Wholesale20
Coupon (269.99 USD): BGJUXT6
(CouponsFromChina.com tip: just apply this code in your cart 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): JX418B, JX418BG, 1B1G1LAP1, LPBF1824, BGX475, aff7off, BGX4539, BGX43539, BGJUX4539, BGXJ4128, BGJUX4X4, BGJUX4X41, BGJUX4X2, BGJUXT1, BGJUXT2, BGJUXT5, BGCITYADS2019
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for JUMPER EZbook X4 4/128GB Notebook is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).