Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (19.20 USD): FBCOUPON1
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): Hardware, TTxBG10, BG2646, BG3088, e3b176, BG2020NS, 0e7f33
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Drip Irrigation Automatic Watering System.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).