Aliexpress
Click here… to search for Xiaomi Aqara Air Conditioning Companion on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
Coupon (32.85 USD): TS15prime
(CouponsFromChina.com tip: apply code in your basket (cart) after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): 20tools, 502C6B, XM15TF, BG1534
(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 Xiaomi Aqara Air Conditioning Companion.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).