Aliexpress
Click here… to search for Digoo DG-MAS1 433MHz GSM Home Alarm System on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon right now! Check this out.
Link: Banggood product page
Coupon (49.60 USD): 13f142
(CouponsFromChina.com tip: this code has to be applied 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): 0404digoo, 502C6B, e2bcea, vipupgrade8, b80ecc, TTxBG10, BGDigoo15%, BG33DGMAS1, BG20COOP, BGKT30GR, bgdigoo15%, AFfbG10, BGMA31, BGMAS129, BGMAS11, BGBFAFF2019, BGCITYADS2019, bGpAnDacHeCk, BGVDay10%off, BGDG15, BGDG110, BGAFF10OFF, bGhOnEy10, 50%DG422, 20%DG422, BGdragonBoat, BGSS10%SW, BGDGASG, BgoFErTaSchInA10, BGHOMEA15%, BgcLuBofErtA10, BGHBHJ105, BGJATD551, BGCuponation10
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Digoo DG-MAS1 433MHz GSM Home Alarm System.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).