Alarm Sound Level: 85dB at 1m, Tolerance: ±3%LEL, Visual Warning: Green: System is on / Electric connection Yellow: Fault / Sensor has lost efficacy, Alarm Set Point: 5%LEL, Material: ABS Plastic, Related Humidity: ≤95% RH, Audible Warning: Speaker(voice alarm), Red: Alarm / Gas Leakage, Power Consumption: <3W, Warm-up Time: 3 minutes(Regular) 10 seconds(Customized), Operating Temperature: 0℃ ~ +55℃, Sensor Type: Catalytic, Detected Flammable Gases: Natural gas(methane) / LPG(liquefied petroleum gas), Operating Voltage: AC110V/220V/230V or DC12V/24V, Area of Usage: Households, Response Time: ≤30 seconds, Dimension: 132*91*39mm, Apparatus Type: Standalone Type / Linkage Type / Networking Type. You can create price alert here, copy coupons and view price history. What is best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
1. ($9.99): BGe825b3
paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/i1u
Old coupons (from the oldest to the newest): Terence, BGKAMAR20, MVC8SPRING, 8BGwbg2204, BG33ecef, BGa87b17, BG5a0905, BGa1f035, BGe9545f, BG5c5e29, BG8ReviTrage, BGeaf456, BG00c906
(probably won’t work, but you can try them out)
Price history and price alert
Price history (for all/most countries) for Combustible Natural Gas Detector is here. The lowest price was: $9.99.
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)).