Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. As you can see I didn’t find any active coupon for this product right now…
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGdb30b1, Kortings10, BGbd3dfa, 2022ACTIESNL, BG21edf9, BG18119c, BG00c906, Terence, BGde7957, BG22c4b9, CouponsdePC, BG959e01, BGa1bc1a, tRaDetRaCKeR, 8wEbgaInS5, BGc3f260, pROMo8cuPoN, hoNEYbGdeAlS, BGJUNEGSG9, BG8ReviTrage, BG0ae934, Cuponation9, BG417a5d, COUPONSDE1wk, BgGoodie9, BG8OFFCOUPON, TTBLACK5, JanBGCoupon8, BGSaleFeb8, BGSaleAD, BG86bd2b, BGcf96f3
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for GMKTEC NucBox4 AMD Ryzen7 3750H Mini PC 16/512GB.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).