As you found out, 512MB isn't much !

I use a Phototainer (80GB) for my portable storage, it has a CF slot built in and will copy, verify, and erase the card contents. It also has a screen to show the images, but I don't waste battery on that
Phototainer uses external batteries which means I can get about 32GB of data onto it with the two batteries I have.

I also have a XSDriveII VP2160 (80GB) as backup, bought while the Phototainer was in for repair
It will copy the CF card, and also has slots for SD and XD. But it does not have a function to verify the copy worked, and it can't be used ot erase the card.
The 2160 does not have external batteries, you have to dismantle it to swap batteries (screwdriver included in the box!) and it uses a standard Fuji battery.