4th Gen ipod dimensions vs 5th Gen / video

I have a 20 GB, 4th generation iPod, which obviously isn't made any more, and all the current 5G models are 30, 60 or 80G, as are their peripherals.

Does anyone know if the dimensions are roughly the same, and I should be able to use the new peripherals, (especially things like snug-fit carrying cases) or have the sizes changed significantly enough that I should troll for 4G stuff?

Thanks!