If you don't do video, you can get away with a ton of CF cards, especially since for many trips you don't 1000x $$$ cards. If you do video it's a bit trickier. If you do Magic Lantern RAW video as I plan to the CF card route is just insane, since nothing less than the very top 1000x CF cards are fast enough and a 32GB card only stores like 7minutes or something and they cost $$$$. You need to transfer so much that USB 3.0 helps. So far the ASUS I mentioned plus a WD passport (all USB 3.0 so that should help speed) seems like one of the few options.
Years ago I used one of those digital wallet with HD, it was very finicky, very, but I managed to both safely store and retrieve everything, it was hairy at times, but not one pic was lost. These days I'd be more prone to getting a ton of slow large CF cards since the cost isn't so bad for that now. Providing you intend to stick to stills or, at the least, avoid doing RAW video.