I have seen hood specialists online that will replace the rear half of the hood only, but I don't think I've seen anyone offering replacements of the window only, given that it is glued and sewn into the back section of the hood.
ah right, I wasn't sure if it was simply zipped on like some soft tops or if it attached permanently. I was going to have a look at an SL, the owner told me there was a couple of splits in the back window hence me asking what the potential cost to fix would be.