Aliexpress
Click here… to search for LANTIAN 24V 16.6A 400W Power Supply on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
Coupon (36.12 USD): Parts8
(CouponsFromChina.com tip: apply code in your basket (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): Charger12, AFfbG10, 502C6B, FBCOUPON1, BGLANTIAN24V, BGAFF10OFF, BGCuponation10, BGBCSpring1, BGDAVIS, BGHONEY2110
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for LANTIAN 24V 16.6A 400W Power Supply.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).