Use a Computer with ICS as a Bridge
This would be a similar approach to the wireless bridge method and could be used by administrators or users. You'd use a computer that's connected to the Enterprise network as a wireless or wired bridge by using the built-in Internet connection sharing (ICS) feature of Windows, included since back with Windows 98 Second Edition. Keep in mind that the computer that's connected to the Enterprise network and the non802.1X device must both have an Ethernet port, so you can connect the two together.
After the host computer has successfully connected to the Enterprise network, you'd enable ICS on that network connection/adapter. To do this you'd bring up the Network Connections window via the Control Panel or Network and Sharing Center. Then you'd right-click the connection/adapter that's connected to the Enterprise network and select Properties.
On the Connection Properties dialog, you'd select the Sharing tab and check the Allow other network users to connect through this computer's Internet connection option. If you have more than one Ethernet adapter on the computer, you'd have to choose which one you want to share the connection with.
Once ICS is set up, any computers or devices you plug into the computer hosting ICS will receive an IP address that's on a different subnet from the Enterprise network. Like the wireless bridge method using DD-WRT, NAT would be used. Thus the Enterprise network is not aware of these non802.1X devices, and the traffic appears to be only from the host computer.