Anyone know of a USB network hub/switch?

I wonder if anyone is aware of a USB network switch/hub? I have some machines which arent upgradable, but come with one NIC and two USB ports. I need to run two seperate physical interfaces(I already have the NIC running as a vlan interface, but I need a seperate interface that isn't vlan tagged). I can, and have, run IP over USB, but that was only between two machines(host to host, ethernet over usb). Im wondering if there is a product which is a network switch/hub but utilizing USB interfaces - any know?

You can get a USB-based NIC, and plug into a normal hub. I've never used one of these with Linux before, so I've no idea what your mileage will be.