Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. I found coupon for you. Check this out.
Link: Banggood product page
Coupon (249.99 USD): BG20ec72
(CouponsFromChina.com tip: coupon code has to be applied in shop’s 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): BG175263, Kortings10, 2022ACTIESNL, BG7b7638, BG44827e, BG00c906, Terence, 8wEbgaInS5, pROMo8cuPoN, hoNEYbGdeAlS, BGJUNEGSG9, DealBGimpact, Cuponation9, BGa7a95c, BG230ebc, BGTKMN15OFF, BGTKMN20OFF, BgGoodie9, BG8OFFCOUPON
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for TRIGKEY Speed S3 Ryzen3 3200U RX Vega 3 Mini PC 8/256GB.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).