I have a feeling that as a vinyl roof was std on the S2 3500s it was an option on the other models!
You should be able to buy all the stuff you need to cover the roof in vinyl for about £60ish.
It can be done in situ,but you wont be able to tuck it under as the originals were!
And as long as its black you wont have a problem getting a pattern match to the 1/4 panels,or just buy enough to redo them as well,so its all as new!!