I have a similar (if not the same) device as D-50, and I love it to pieces, except the battery life, I have been battling the battery life since day one. I am planning on taking a similar trip in which I will be removed from technology in general, in which I am planning on bringing a 2GB card, 1 GB card, an Epson unit (the portable HD) for carrying with me on the street, as well as a laptop where I plan on loading my images and making a discs of my images to pack in seperate luggage. Perhaps it is alot to bring, but I am just hoping that my camera doesn't crash, and other than that I have everythign else backed up (two memory cards unless one corrupts, 2 hard drives etc.)
Good luck with your hunt for memory cards