Although there are many mini-usb drives now, this credit card size 8GB USB drive might do the trick of hiding safetly and discreetly in your wallet.
‧ 3mm Thin (Aluminum Alloy Casing )
‧ Retraction Connector
‧ Mobile USB flash drive, USB 1.1/2.0 compatible
‧ Hot swappable, USB Plug & Play compatible
‧ LED access indicator with three modes: Busy, waiting, and off
‧ Carrying caddy for easy storage in your wallet
‧ Built-in personal customizable software (USB Notebook Professional)