alanint is correct. These models were created to prevent the insertion of real parts, and to make sure toy parts were not used in a real pistol. Either of those conditions would have been dangerous and would lead to a disaster. If you need toy (replica) parts, you will have to find a source for the replica parts. Perhaps even find another replica Luger of the same vintage that has the parts you need...
Put an active search on eBay to find what you are looking for so they will email you everytime something that matches your search is posted. Here is an example. I see that even parts guns (replicas) are not cheap!
http://www.ebay.com/itm/Luger-P08-Pa...oAAOSwzWpZkNr5
It might be easier to just buy a modern replica, or take up machining as a hobby and make your own parts.