Thank you for your suggestion, Petar.
Though using RadListBox will be a too much of a rework, as plain silverlight listboxes are being used at multiple places in the application I have. Even most of the other controls are silverlight controls which are consistent with the look and feel. As only RadTreeView control has a different appearance, changing it is only my option for now.
I tried to follow http://msdn.microsoft.com/en-us/library/cc278065(v=vs.95).aspx
for my use, but I am yet to figure out how would I go about it.