I've used PCI cards that'll let you drop a PCMCIA card into them, I've never seen a USB version. don't know why they wouldn't be out there though.
really, the throughput on a wireless card isn't that much more than a USB interface can handle (even closer if you use the 1394/firewire or USB 2.0 setup)
you've actually got several options here as I see it.
PCI to PCMCIA adaptor: $60
PCI wireless network card: $80
USB wireless network card; $60
it just depends on your budget, and what your ultimate goals are.
personally, I got a 3-COM wireless PCI card. (put me back about $100) it had an external antenna, that let me place the recever in an optimal spot, as opposed to having to place my entire tower in an optimal spot to get a decent signal. (not all signal locations are created equil... and one bar difference may not be a big deal for checking e-mail, but downloading anything larger than a meg becomes downright painfull if the bandwidth falls far enough.)
if you are a fan of newegg, here are some links to stuff I found there:
a USB wireless adaptor
http://www.newegg.com/Product/Product.asp?Item=N82E16833130111a PCI wireless adaptor
http://www.newegg.com/Product/Product.asp?Item=N82E16833314012a PCI to PCMCIA adaptor
http://www.newegg.com/Product/Product.asp?Item=N82E16815124021I didn't see any USB to PCMCIA cards on that site... though...
just the other way arround. (to get extra usb slots via your PCMCIA laptop)
if you really want to use your current card, I'd just go with the PCI version (linked above) if you've got a free slot.
let me know if you have any questions.
-RuskiFace the Pirate