Should be at CDG according to the rules if hand luggage only, but not if the bags are checked. I would try at TXL as you can get the stamp before departure and I doubt you need to show evidence that you checked a bag. If that fails and you can't get the stamp at CDG, Some countries consulates also provide the stamp (not sure about Germany). Lastly, you have three months to get the stamp. So if you take it back to Europe and have receipts you can do it then (I have).