Where do you buy Zen in Neverwinter?

I'm curious, where exactly can one purchase Zen in the virtual world of Neverwinter? Is there a specific in-game marketplace or exchange where players can safely and securely acquire this digital currency? Perhaps there are also real-world options for those looking to enhance their gaming experience with a little extra financial boost. I'm eager to learn more about the process and the best practices to follow when making such a transaction.