I don't get exactly what you mean. Do you mean a firewire card that plugs into USB? Or one that plugs into a PCI slot but has USB extensions too?
This is a link from that site of the Firewire 800 that plugs into a PCI port and allows only Firewire ports which would work.
EDIT: Oh sorry. Those pics didn't load up at first. I'll have a look.
Wouldn't those just be Firewire to USB though? So you wouldn't get the speed increases of firewire, and I don't think Firewire devices would work in the same way as if you got an adapter.
I'm not sure on this though, but that adapter just seems to be if theres a device with only Firewire functionality that would work through USB