I have just checked coupons. The lowest price I could get is $16.99 for Solar Charging Bike Headlight 400lm (in Banggood). Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Solar Charging Bike Headlight 400Lm Brightness 200m Distance Range 2000mAh Battery Waterproof 3 Light Modes Warning Flashlight with 130dB Horn for Road Mountain Bicycle
Latest coupon code price check (UTC time):
Banggood ($16.99)
Banggood warehouse is located in China. Too bad there’s no coupon right now in Banggood. Is it cheap? Hmmm, price is higher than average (which is $8.89 right now), so better set price alert down below…
Link: Banggood product page
Price: $16.99
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for Solar Charging Bike Headlight 400lm.
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)).