Aliexpress
Click here… to search for Xiaomi Yeelight YLDP05YL & YLDP06YL E27 LED Bulbs on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
Coupon (38.37 USD): bGhOnEy10
(CouponsFromChina.com tip: this code has to be applied in your 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): BGTLJ1, AFfbG10, BGYEE11COU, BGVDay10%off, BGLIGHT2020, BGdragonBoat, BGSS10%SW
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Yeelight YLDP05YL & YLDP06YL E27 LED Bulbs.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).