You can create price alert here, copy coupons and view price history. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
repelling ultrasonic frequency is 22 – 65KHz and the effective range is 80 – 120sqm
Banggood
Banggood warehouse is located in China. I have no active coupons for you right now.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGLOS07, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, BGBGHFRI15, BGVDay10%off, BGHOMEG12, BGMPB2020, BGWIUQEF, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, BGHome15%, BgcLuBofErtA10, BGHONEY2110, BG10OFFAFF, BGwhielabel, 13f142, BG10OFFAFF1, BANGGOODSD
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Electronic Pest Reject Repeller is here.
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)).