There's no way that you can get the original voices from your DOTT CD. Although I think the monster.sou (is it?) file is only about 200 or 300 MB in each version it's only available in the respective language version of the game.
You've gotta get the English version of the talkie. Maybe some future incarnation of the Entertainment Pack will feature DOTT and you could get it at OkaySoft
or some other source for imports. If you have PayPal or other methods of international payment you can try the international search on eBay.de