Hey there,
On my old Z3, I hated the line that developed in the middle of the 'window' because of the fold. I ended up buying a new zip in window off eBay, and then I had Wynberg Upholsterers fit it for me. Was a massive improvement in the look of the car, as well as the ability to properly look out the back window!
Think it was about $100 at the time, and Wynberg didn't charge too much to fit, but at least I knew it was done properly. Definitely worth doing, and not tooooo pricey.
I would have thought a whole new top would have been way more costly/complicated, etc?
Good luck!
Pete