Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. Well, there is one coupon available right now.
Link: Banggood product page
Coupon (46.74 USD): BGWDT15
(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): BG4c87d9, BG02cf64, BGWT15
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for 90 Degrees Positioning Ruler L-Type 160x160mm Suit is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).