Aliexpress
Click here… to search for Beelink SER4 4700U 16/500GB Mini PC BT5.2 on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
Coupon (436.79 USD): Cuponation9
Coupon (436.79 USD): BgGoodie9
Coupon (441.59 USD): BG8ReviTrage
(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): DealBGimpact, BGf224cc, BGf8b641
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Beelink SER4 4700U 16/500GB Mini PC BT5.2.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).