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 (327.59 USD): 7bcdf9
Coupon (327.59 USD): 7BCDF9
(CouponsFromChina.com tip: apply code in your basket (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): elec, BGCITYADS2019, bGpAnDacHeCk, bGhOnEy10, BGAFF10OFF
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Beelink L55 i3-5005U 8/512GB Mini PC is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).