Wont let me download same in app purchase on a different device

I bought an in app purchase on my ipod. It was the voice pack for ispeech. I went to my ipad later, tried to download it again, but it says i need to pay. Its on the same account, but it wont let me... Im starting to lose my temper with this. Im not paying again because a company is being cheap. I would like to know how to redownload it, or i would like apple to give me $2.99 to purchase it again on the same account.