You mean like a save game editor that adds inventory items? I dont think one exists, but Im probably wrong. You could just add the items you need on a map you havent been to and go there.
Yeah, no there is no editor out there that can do that. The best you can do is turn an item into something similar. The best bet you got is probably what Xavierblazer said. Edit the map and place whatever you want lying on the ground or in a book case.
The Fallout II Savegame Cracker does this. You can find it in the files section. Don't know if it's 100% bug-free, though. If not, I've usually been able to use the old inventory editor that swaps items to get what I want.