can you re-buy music from a used but loaded ipod

Now that ipod's are collectors' items, is there a way to keep BUT re-buy music that you found on a used IPOD?

Wifey and I are looking for bigger storage ipod's and some may actually have music that we wish to keep. I am VERY aware of the legalities. I thought there may be a way that iTunes will prompt you that "this song is not found in your account, do you wish to purchase it?"