Here's a USB-to-Ethernet (plus three-socket USB hub) from a place in Seattle that makes custom cables. I don't know the chipset or anything, and I decided I'm better off with a Travel Router for my purposes so I haven't bought one; but they deal on the internet, and at least locally they offered to let me bring it back if it didn't work with the N800. Here's the product page. I think it at least looks good.