Make a new mall item called Item Restoration. This will take manual work on the GM's part but this item should be very expensive to compensate. I would say 5000RE or more.
The purpose of the mall item is to allow players to restore any item that was destroyed through combination without enough items (say use 2 G4's to make a G5 and it fails), breaking due to durability, or deleted due to character deletion. We've all had stupid moments where we accidentally don't watch the dura of an equipment while level/pvping with it and it breaks or we delete some extra char on our accounts and forget something valuable was on it.
Since this item will be very expensive, it won't be abused too much and it should bring in some extra money to the server.