Just check coupons out (with price alert and history). What is best price?
Cree XP-E, 350 lm, Battery Quantity: 1200mAh 16340 battery
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest coupon and price update (UTC):
Price history and price alert
Here is price history (for all/most countries) for XD-Z501 Flashlight.
Price records source(s): Gearbest
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)).