When I was updating this page the price was $39.99 for 2 Layer 300W Portable Electric Lunch Box (in Banggood). Basically copy coupon, view price history or create e-mail price alert. You probably want to know what is the best price?
2 Layer 300W Portable Electric Lunch Box Food Warmer for Travel Self Cooking Heated Lunch Box for Home Office Cooking Food – Green
Latest price update (UTC time):
Banggood ($39.99)
Banggood warehouse is located in China. What about the price? Actually this is the best price in history according to CouponsFromChina database! One coupon is available. Cool!
Link: Banggood product page
Price without coupon: $42.99
1. ($39.99): BG9c40c7
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Aliexpress
There’re some similar (or not) items on Aliexpress
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 2 Layer 300W Portable Electric Lunch Box.
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)).