I have a National Instruments card which is an older interface - PCMCIA Type II PC Card.
Naturally, my laptop I would like to use this with does not have a PC Card slot (only USB and Express Card 54).
I have been able to find literally hundreds of adapters to take a PC Card slot and use it for everything but nothing going the other way.
If you do not need to move around much you can combine an express card to PCI-e adapter and combine that with a common PCI express to PCMCIA adapter.
The nice thing about this is that it is a very flexible solution, allowing you yo use common PCI-e cards (including PCI-e to PCMCIA, or even PCI-e graphics cards).
The downside it that it is not very portable. If you only need the PCMCIA card at one location you could use this and just unplug the card. If you need it in the field it becomes unwieldy.
Note that technically this is relative trivial since express card basically is a single PCI-e lane and a single USB connection. However you will need to find the right drivers for your PCMCIA card. That might be a challenge on modern OS's (PCMCIA is based on old ISA. That thing from the IBM XT time).
There are several USB-based PCMCIA adapters on the market. A quick google search for external pcmcia usb adapter turns up a number of them.
Amtron seems to offer a number of USB-based readers, including this one which looks to support a number of different card types.
There also seems to be some for dedicated purposes, like using 3G modem (see here)
I know this post is rather late...I'm not sure if you found a solution to your problem or not. I too was in a similar predicament but solved it by buying a Startech CB2EC PCMCIA 2 to Expresscard adapter! It is plug & play,hence recognized & installed at once & working perfectly! There are many brands of this card & these are freely available. However the Startech card is known to be very stable & you should be able get one for about $ 35.00 including postage, but beware as some venders are charging twice as much for it!
Good luck!
In addition to the other answers, if anyone else finds this site, you can find Expresscard to PCMCIA adapters as well. These are generally considerably cheaper.
This one:
works with both 32-bit and 16-bit cards but is limited to Windows and will work in my situation. Other cards may not support both 16/32bit cards (make sure to check before purchasing) or specific operating systems.