Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (229.99 USD): BGa80bee
(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): BGc9577a, BGf7dd8e, BG54073a, BGa59382, BG63ddf0, BG6849d3, BG8efceb, BGdaee69, BGAUGUST8, BGa0dcc9, BGCAPITALOS8, BG29f140
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for Beelink SEi8 i5-8279U 8/256GB Mini PC is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).