Used to use a portable hd Archos... But the brand went downhill as the years passed including not caring for customers.
I believe there are still a few hd type things like this around, just need to look for them. Usual price around 250ukp upwards for 250gb.
Used to use archos 5 with an (optional) extra plug in you could pretend it was a computer and offload all the images (usually whilst eating in a restaurant) to clean the card ready for an afternoons shooting.
One thing to make sure before you delete is that it copied all the files, hopefully ok...
A lot lighter than a laptop. Just needed to be charged whilst you slept.
However, can't use it now as the battery leaked (after 4 years).
Memory Cards are pretty cheap now, but you'll need a nice pouch to keep them in and separated from the used to the ready to use...