Aliexpress
Click here… to search for Petree Self Cleaning Cat Toilet on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (423.19 USD): BG8OFFCOUPON
Coupon (432.39 USD): BG00c906
(CouponsFromChina.com tip: this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): BG7c716c, BG58e9cf, hoNEYbGdeAlS, BGJUNEGSG9, BG8ReviTrage, Cuponation9, BgGoodie9, BGcoupon8off, BGGutscheine
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for Petree Self Cleaning Cat Toilet is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).