Personally don't know of a smaller card. However, I was having same issue with my Version 1 system. Case was only 3 inches tall and cards were taller. I opted for a pci riser which came back over the motherboard (as opposed to the ones that go and cover the pci slots)from Barada (http://www.barada.ca/eng/index.htm), and a data chute. Card is tall. But since there was no external connection, it didn't matter in my case. With the Data Chute (by Antec) I can run any pcmcia card on my system. This is great for using any wifi, wired nic, pcmcia scanners, pcmcia card readers, etc.... Basically I now have a verychangeable system without taking anything apart. Push a button pop one card out , and put another in.
Hope this gives you an alternative, if you cant find a smaller card.