Color rendering index: Ra80, Product size: 43x112mm, Color temperature range: 2700K-6500K, Voltage: AC220V 50Hz, Brightness range: 5%-100%, Product name: Yeelight color temperature bulb M2, Luminous flux: 450LM, Power: 4W, Standby power: 0.5W, Screw model: E27, Product model: YLDP26YL.
Basically copy coupon, view price history or create e-mail price alert. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGYEE20COUPON, BGLIGHT0920, BGELIG0920, BgcLuBofErtA10, BGYEE2021, BGCuponation10, BGYEEL10, BGHONEY2110, BG10OFFAFF, BGwhielabel, 13f142, BGLIG12, BG10OFFAFF1, BGYEELIGHT21, BGd0b05d, BG2589f4, 00c906
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for Xiaomi Yeelight YLDP26YL M2 Color Temperature Smart Bulb E27? There we go. The lowest price was: $11.33.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).