Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (4.49 USD): BGf94f14
Coupon (4.67 USD): FIN7053
(CouponsFromChina.com tip: put item in your cart and apply coupon code there 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): BGtorch2, BG166LT, BGbdcf25, BGHDW16, 2203ActiesNL, BG1efeb0, MVC8SPRING
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Astrolux 1.6x6mm Luminous Tube for MF01X Flashlight is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).