Kuroutoshikou releases Excard-LPCIE: a low-profile PCI Express x1 add-in board with an ExpressCard 54 slot. There's a USB 2.0 port on board for good measure.
If you want to connect it to your desktop PC, then Kuroutoshikou wants a mere ¥4,980 ($43/£23) for the Excard-LPCIE