Looking For Portable Ethernet Hubs?

Lynk asks: "I often have to network a couple of machines (normally 2x laptops and a palmtop) together and sometimes into a client's network, too, so I've been looking for a suitable Ethernet Hub. Nice and small so I can carry it about in my laptop case but without a PSU twice as big as the hub. Four ports is fine. Preferably battery powered. I have used x-over cables a bit but they eliminate connecting to a client's network. Anyone have any ideas or have done this already?"