I was about to start writing a tool to do this when it occurred to me that someone else must have done this already. Googling located two solutions:
Of these, (1) seems to be out of date and doesn't handle .NET 2.0, so it's no good to me at all. Option (2) appeals the most because it's an addin for Reflector. Trouble is, the current version of Reflector won't load it! I haven't time to work out why, but looking in the Google code issue list for this project, someone has reported this error already. Would be nice to see this fixed. I'd quite like to write code to do the reflection + generation myself, but it's just a distraction I can't afford right now.