Black door panels (embossed cardboard) are available.
Or, paint the cardboard whatever color you want.
Or, follow Tim's (SW_Radial) advice above and use 3-M spray glue to attach whatever covering you want. I bought seat cover material and glued it on the side panels in my Suburban, because the original color panels are not available.
The advantage of attaching to a metal or Plexiglas base, rather than the cardboard base, is that you will not get water warpage. Some people have reported coating the back of the cardboard panel with marine spar polyurethane varnish to help reduce/stop the warpage.
Tim
