Mosquito Bite Helper (Banggood, Aliexpress: Weight: 80g, Color: Cool Black, Battery: 1x AA Battery (Not Included), Material: ABS, Size: 160x 29mm / 6.3″x 1.14″, Rated Voltage: 5V (the best price with coupon)).
Price history, coupons and price alert are available on this page. Let’s see what best price is ATM.
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. Well, there is one coupon available right now.
Link: Banggood product page
1. ($8.09): AFfbG10
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 684fa7, e2bcea, TTxBG10, 2019SPEDM, BGITCH544, 502C6B, BGBFAFF2019, BGCITYADS2019, BGBGHFRI15
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for Mosquito Bite Helper is here. The lowest price was: $5.44.
Price records source(s): Gearbest, 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)).