Hey Edmund,
Have you had any luck? As one of the replies here states, this link will get you to a webpage that can give a list of USB Ethernet adapters that are compatible. Let me know if this helps.
If you look at the list, even the ones marked "compatible" do not have any "compatible" votes from the community, with the exception of the Cisco USB300m. I believe that of the 31 devices listed there, none are compatible with surface, regardless of whether
MS erroneously lists it as compatible.
What appears to be happening is that "incompatible" votes are strangely relayed. As an example, the Cisco USB300M shows 2 of 14 votes for compatible. I believe that the 12 votes that are not for compatible are votes for incompatible. With the exception of
the Cisco device, all of the Ethernet USB devices listed show no votes or "0 of xx" votes for compatibility - In short, nothing works.
Personally, I have purchased both the Cisco USB300M and the Trendnet device based on Microsoft's listing showing compatibility with RT - neither works on a surface.
As a user, I think this is a completely unacceptable situation. If USB Ethernet devices aren't supported (as http://blog.premiumusb.com/2012/10/usb-drive-port-yes-ethernet-cord-no-on-microsoft-surface/ indicates), then MS needs to be up front and say so.