Go with an original all the way. The ONLY way to go. We've put a roof in one car already, it was cake. We're about to do another.
Believe it or not, but try posting a wanted ad on the samba. Those things work, my buddy posted one about slide roofs and he's found 2 or 3 I think, but I doubt he'll sell them.
I asked earlier tonight. He'll just sit on them incase he needs them for another project.