Aliexpress
Click here… to search for UNI-T UT300S Infrared Thermometer on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
Coupon (14.87 USD): AFfbG10
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): 502C6B, 2019SPEDM, BGBG4683
(these coupons are old, so probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for UNI-T UT300S Infrared Thermometer.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).