For a Duo, you can get one of the following:DuoDock with onboard AAUI and an AAUI-to-RJ45 transceiver or an ethernet Nubus card with a RJ45 port. This is the largest and most easily obtainable option, though can only be used as a desktop.
MiniDock with a RJ45 ethernet port. This is a medium format and slightly harder to find solution. Portable, but still a desktop format.
EtherNet Microdock - The smallest variant, this keeps the Duo as a laptop, but is very rare. I paid $35 for mine, which was cheap, as I've seen them go for over $50 on eBay.
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