We have ever used some PCMCIA to PCI adaptors, they are working properly with NI PCMCIA-FBUS card as well as NI-FBUS software.
I'd like to recommend the single CardBus PCMCIA slot adaptor from Elan Digital System:
We have used the adaptor in a Dell Dimension desktop, running XP SP2, and NI-FBUS Configurator 3.1.1 runs well.
Another adaptor is a long card, which is Gigabyte GA-MPCI, it works well with some old desktops, but the length of the card is about twice of the card of Elan Digital System; it might not fit your requirement.
Hope it helps.