Aliexpress
Click here… to search for Xiaomi Black Shark 3 12/256GB Global 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 (652.00 USD): Email5
Coupon (652.00 USD): BGHALLOWEEN
(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)
Old coupons (from the oldest to the newest): BG5BS312, BG9BS312
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Black Shark 3 12/256GB Global.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).