Xircom/intel Realports are no longer available new but work really well on Linux and have the advantage over others that there is no dongle thing hanging out the side the ethernet cable plugs straight in.
They can usually be found for next to no money on ebay.
However you need 2 PCMCIA sockets to accommodate the height, if you have two release buttons (one above the other) then you have a dual socket and therefore can accommodate one of these.
I have had success with little or no effort with various USB ethernet thingies, but sadly cannot tell you which ones as they were unbranded el-cheapo purchased in an emergency from a local computer shop.