Behaviour to simulate an enum implementing an interface

Say I have an enum something like:

enum OrderStatus
{
    AwaitingAuthorization,
    InProduction,
    AwaitingDespatch
}

I've also created an extension method on my enum to tidy up the displayed values in the UI, so I have something like:

public static string ToDisplayString(this OrderStatus status)
{
    switch (status)
    {
        case Status.AwaitingAuthorization:
            return "Awaiting Authorization";

        case Status.InProduction:
            return "Item in Production";

        ... etc
    }
}

Inspired by the excellent post here, I want to bind my enums to a SelectList with an extension method:

public static SelectList ToSelectList<TEnum>(this TEnum enumObj)

however, to use the DisplayString values in the UI drop down I'd need to add a constraint along the lines of

: where TEnum has extension ToDisplayString

Obviously none of this is going to work at all with the current approach, unless there's some clever trick I don't know about.

Does anyone have any ideas about how I might be able to implement something like this?