It will be much easier to find CF WiFi cards with Pocket PC drivers, though check to see that they offer drivers for the older Pocket PC 2000 OS. I seem to recall that the Ambicom and Socket CF cards reviewed on this site have PPC 2000 drivers.
The Sierra Wireless AirCard like the 555 reviewed on our site works well, though I'm not sure their drivers go back to the PPC 2000 OS.