Some exchanges allocated Symbol to their customers and a few of them listed Symbol for trading. I gave you list of them but if you want to get more updates, please follow Twitter account of NEM: https://twitter.com/NEMofficial

List is there: https://www.coingecko.com/en/coins/symbol
I would prefer to use Coingecko to get updates than Coinmarketcap tracker that is more slowly updated.

https://coinmarketcap.com/currencies/symbol/