Latest update shows that Portable Cordless Neck Heater costs $17.99 (in Banggood). Just check coupons out (with price alert and history). Let’s see what best price is ATM.
Portable Cordless Heater Neck Heater Personal Wearable Electric Heater 4-Speed Temperature Cordless Charging Personal Heater Outdoor Heater – Grey
Latest coupon and price update (UTC):
Banggood ($17.99)
Banggood warehouse is located in China. But wait a sec… Is it a good price? Well, according to CouponsFromChina database this price is the best in history (2 records). Only one coupon available!
Link: Banggood product page
Price without coupon: $22.99
1. ($17.99): BGdd97c4
you should apply the coupon in your cart 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 Portable Cordless Neck Heater.
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)).