Where can I find DVD slipcases/slipcovers for sale?

I was wondering if there were any websites that sell the slipcases/slipcovers for DVDs. I own several DVDs that originally came in slipcovers but then did not after they had been out for a while, i.e. The Da Vinci Code, The Devil Wears Prada, and The Grudge Unrated Extended Director's Cut. Does anyone know if someone sells the actual slipcovers to DVDs when they were first released? I would really love to have these movies' covers if they are available, because slipcovers make the DVD look even better. If anyone has any information, it would be HIGHLY appreciated!