It's right in the .zip file with the map, in the 'overviews' folder.
I didn't make it like the standard ones, there are no textures, it's more of a floorplan. I think it's easier to look at.
I don't know if I'm crazy but it appears Valve removed the ability to make overviews in 1.6. The commands to do it don't work, like you said, anymore