Express Card is NOT the same as a P2/PCMCIA slot - you'd need a laptop with an older PCMCIA/PCCard slot.
This is based on the information found in the wikipedia article on P2 stroage:
"The cards can also be used directly where a PC card slot is available, as in most notebook computers, as a normal disk drive, although a custom software driver must first be loaded."
http://en.wikipedia.org/wiki/P2_%28storage_media%29You can get adapters, but I suspect they are just as big as your reader.
http://sewelldirect.com/Express-Card-to-PCMCIA-Adapter.asp