I was at my local public library today and happened to stumble across Nicholas Meyer's book "The View from the Bridge," about his work on the Trek films. In the photo section, lo and behold, was the picture I'd been looking for!
When compared to this small model from TMP, you can clearly see that it's exactly the same, even right down to the cradle where the workbee would have been:
The fourth cargo pod has mostly sunk into the sand, but it's there. You can even see two of the old-style UFP logos on the sides of the containers. So now we have irrefutable proof that they were not in fact from the Botany Bay.