Just check coupons out (with price alert and history). Do you want to know what the best price is?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Net Weight 272g, Charging Time 3.5H, Rated Power 5W, Material PC + ABS, Input DC 5V/1A, Battery Capacity 3.7V/1200mAh, – Diamond Lampshade with Anti-skid Silicone Pad, – 0-300lm Stepless Dimming, Working Time 3H, Lifespan 50000H, Working Temperature 0 – 40°C, Dimming Type Touch Control, Color Temperature 3000K, Lumen 300LM, Power Interface Micro USB, LED SMD2835x 26Pcs, Battery Type 18650 Li-Battery, Dimensions 139x 139x 128mm / 5.47″x 5.47″x 5.04″, – Innovative Look & Touch Sensor Control
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($17.99): BGHome15%
2. ($18.89): BGAFF10OFF
3. ($18.89): bGhOnEy10
4. ($18.89): BGHOMEA15%
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGss10%bw, AFfbG10, BGLT19304, BGBWLT19, BGLT1911, BGDKS11, BGBWLT19Light, BGBWLT199, BGBWLT899, BGTY2K, BGVDay10%off, BGHOMEG12, BG85433T, BGBW152, BGdragonBoat, BGSS10%SW, bgshOOp10, BGSMARTBUYT19
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for BlitzWolf BW-LT19 Diamond Night Lamp.
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)).