Here are some images with links. Also any Christian bookstore should be able to order you one.
http://images.google.com/images?q=star+of+david+with+cross&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&ei=XA-XS83PMZPysgO93LHCAQ&sa=X&oi=image_result_group&ct=title&resnum=1&ved=0CBwQsAQwAA
WOW!