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 (540.89 USD): bGhOnEy10
Coupon (540.89 USD): BGUYSH
Coupon (540.89 USD): BGTT10
Coupon (540.89 USD): BGJUNS2
Coupon (593.99 USD): Email5
(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): BGHY156, aff7off, BGHY2794, BGS20087, BGSA208, BGSA204, BGSA205, BGHYST200, BGSA206, BGSA207, bgchinafest, BGHYST88, BGHYST99, BGJPHYST99, BGHSTS200, BGBFCR29, BGHYST100, BGCITYADS2019, BGHYST101, BGBFHYS1, BGHYST102, BGHY103, bGpAnDacHeCk, BGHY105, BGHY106, BGHY108, BGNY108, BGHY109, BGHY116, BGHY118, BGHY119, BGMYSH, BGSTHY, bgshOOp10, BGEMS20, BGTOMS, BGCTQG, BGQGCP, BGUSAS2, BG11MN25
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for HYSTOU S200 i7-8750H 16/512GB Mini PC.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).