Protected, Battery: 18650, Rechargeable: Yes, Protected: Yes, Practical Capacity (mAh): 3400mAh, Voltage(V): 3.7V, Package Contents: 4x NCR18650B 18650 Li-ion Battery.
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.
Updated:
Banggood
Warehouse in China.
Link: 4x Panasonic NCR18650B 3400mAh Protected Battery
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:
1. First page
2. Second page
Price history and price alert
Price history (for all/most countries) for 4x Panasonic NCR18650B 3400mAh Protected Battery is here. The lowest price was: $14.99.
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)).