I believe 500 carpets will fit.
The one piece is ok but requires some modification, Jan-in-UK did put one of these 500 carpets into a 126 aircooled, he would be able to tell you the mods he did.
On e bay UK there are some sellers of carpets.
Other than that try axel gerstyl for original parts, see the reputable companies part on this forum.
While you at it, you can get me two, black
Just kidding