Lowest cost: $11.99 via Banggood. Stainless Steel 316 Smart Thermal Cup with Intelligent Temperature Display 450ml Capacity Perfect Office Coffee Mug Portable with One-Button Flip-top Lid Ideal for Travel – #01.
Updated:
Banggood
Warehouse in China.
Link: Stainless Steel 316 Thermal Cup with Temperature Display 450ml
Price: $11.99
Additional Banggood coupons:
1. First page
2. Second page
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Check out price history chart (for all/most countries) for Stainless Steel 316 Thermal Cup with Temperature Display 450ml. The lowest price was: $8.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).