Anything larger than 4GB for SD cards, are made in an SDHC version, which is a diff format than the standard SD format.
Flash (or thumb) drives go pretty cheap for 32 or 64 GB storage, but generally are more expensive than portable (or external) hard drives of the same size.
Western Digital makes portable hard drives the size of your wallet in sizes of up to 250GB, and use USB (although you can get some in FW400) connectors.
Best Buy (
www.bestbuy.com) and Fry's Electronics (
www.frys.com) generally carry these products with great prices.
Hope this helps! Good luck...