Rated Frequency 50Hz/60Hz, Material ABS, Hand Warmer Energy 8000KJ, Rated Voltage 85-265V, Color Pink, Hand Warmer Size 70*27.5mm, Rated Power 400W, Hand Warmer Weight 80g, Product Size 144*148*128mm, Product Weight 485g.
You can create price alert here, copy coupons and view price history. Best price?
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.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($26.74): BGHOMEA13
2. ($27.73): BGAFF10OFF
this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): d8414b, Hardware, TTxBG10, aff7off, bgssaff9, AFfbG10, BGhardware, BG2756, BG2020NS, BG6390, BGMPB2020, bGhOnEy10, BGdragonBoat, bgshOOp10, BGHWDEALS, BgoFErTaSchInA10, BgcLuBofErtA10, BGHap20
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Happy Life Detachable Hand Warmer Pink. The lowest price was: $20.29.
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)).