0.300~1.000: Moderate, Item size: 164 * 74 * 26mm / 6.5 * 2.9 * 1.0in, 0.100~0.300: Slight, 0~0.100: Fine, O₃ concentration AQI: , Color: black+orange, 1.000~4.999: Serious, Material: ABS, Package size: 280 * 225 * 70mm / 11.0 * 8.9 * 2.8in, Package weight: 501g / 1.1lb, Battery: 1 * lithium battery / 2000mAh (included), Screen size: 2.8in.
Basically copy coupon, view price history or create e-mail price alert. 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 code price check (UTC time):
Banggood
Banggood warehouse is located in China. I have no active coupons for you right now.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGGines
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for Ozone Analyzer Meter Sensor. The lowest price was: $75.99.
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)).