I apologize for the inconvenience.
We are actively working on getting an active marketplace offering up and running. Stay tuned.
In the meantime, please feel free to sign up for a trial on our website. The NuGet package available here: https://www.nuget.org/packages/AppDynamics.WindowsAzure.CloudServices/ can be used to download and install the agent with the instructions available here: https://docs.appdynamics.com/display/PRO42/Install+AppDynamics+for+Windows+Azure+with+NuGet
Regards,
Meera