There are a number of CGMs on the market.
Libre is the most common because it is the cheapest.
Dexcom is the next cheapest and popular. For people with Type 1, Dexcom is preferred over Libre as it is considered more accurate.
Medtronic have one which I think is called Guardian.
Medtrum have one which can be linked to their insulin pump.
Eversense is implanted for up to 90 days.
You question is rather broad and does not explain the purpose. Can you elaborate - are you looking for yourself, are you looking for alerts, have you check Google (there are a number of sites that list CGMs), where are you based? ...