Aliexpress
Click here… to search for GauTone PG107 4.3inch Security Alarm System on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (93.53 USD): Cuponation9
Coupon (93.53 USD): BgGoodie9
(CouponsFromChina.com tip: you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGa47596, BG4a7a54, ADMITAD2212, BGSmart6, Couponsde7, BG75639a, BG7baf16, BGe4b286, hoNEYbGdeAlS, BGJUNEGSG9, BGe7adee, BG815f7e
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for GauTone PG107 4.3inch Security Alarm System? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).