Aliexpress
Click here… to search for Astrolux A02 SST20 Keychain Flashlight on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (16.99 USD): FIN4071
Coupon (18.44 USD): BG8Alerabat
Coupon (18.44 USD): BGOutlight10
(CouponsFromChina.com tip: coupon code has to be applied in shop’s 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): BGA02, BGASTROLUX, BG1128, BGAST25, BGSM30%, BGASA02, FIN7140, BG10OFFAFF1, BANGGOODSD, BGTorch4, BGASTB, BGXMAS58, BGAlerabat15, BGtorch7, BGtorch2, BGAlerabatI, BGASTC, BGea6033, BGLED07
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Price history (for all/most countries) for Astrolux A02 SST20 Keychain Flashlight is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).