Aliexpress
Click here… to search for MGCOOL Band 3 Smartband on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
Coupon (14.54 USD): band10
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply 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): e2bcea, TTxBG10, 2019SPEDM, BG3CSUM
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for MGCOOL Band 3 Smartband.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).