We couldn't reproduce your issue. We get all the RadControls for Silverlight with the installation. Can you try re-installing the suite and let us know if the problem still exists. Also you may share more info about the version of the suite you're using, Windows version, Visual Studio version and so on.
Thank you for your cooperation.
On a side note - if you reference the Telerik.Windows.Controls.dll and add the needed namespace in the XAML - you'll be able to use the Exander for sure.
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