rear plastic roof

The rear window for the convertables is available on eBay. The prices vary, but generally speaking, they go for about $200 (USD).

Here, this is in the UK.

You're welcome.

Also, the rear window on the E36 has a zipper. I haven't replaced my window yet, but I did find the zipper. My suggestion is to get the new window in the mail and look at the zipper to get an idea of where the Zipper Pull is and how it works. I'm not sure how it works, because the Zipper Pull seems to be missing from my window. Maybe the Pull comes off when the window is installed, I don't know. There is no need to take the window out except for replacement, so it makes sense that the Pull might come off when the window is installed completely.

By all appearances, I see no reason why one can't replace the rear window at home. It looks like it might take two people, but there is no sewing or removal of the roof, or anything along those lines.