Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
Coupon (193.19 USD): BG8OFFCOUPON
Coupon (197.39 USD): BG00c906
(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): BgGoodie9, BG8ReviTrage, BGcoupon8off, BGGutscheine, BG483866
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for TRIGKEY Green G3 N5100 8/256GB Mini PC.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).