Anything is possible, but the Hardback and Wagon have completely different design parcel shelfs. The Hardback has a solid parcel shelf, but the Wagon uses a roller blind type.
It might be possible to fabricobble something together, but it won't necessarily work or look good. I know of a couple of Hardback owners that made their own parcel shelves from scratch out of thin plywood, covering them in automotive carpet to match the interior colour. Doing this should give you a satisfactory finish, but at a fraction of the cost of a second hand OE one.