Do you still have the items in your iTunes library on your computer? If so, just sync them onto your iPod.
If you don't have them on your computer, and the items are songs, you can open the iTunes store, and on the right sidebar there will a thing that says, "Quick Links". Under that it will say "Purchases". Click that and it will take you to all your purchased songs off the iTunes Store.
If the items are movies, the process is more complicated. Post back for more info if that's the case.