WARNING: THIS IS DANGEROUS RISKY STUFF AND SHOULD ONLY BE DONE IF THERE IS NO OTHER WAY TO ACCOMPLISH WHAT YOU NEED TO DO. PROCEED WITH CAUTION AND AT YOUR OWN RISK. AND DON"T MESS UP YOUR APERTURE DATABASE. I sort of understand why Apple makes this hard but why have "Reveal in Finder" built in to iPhoto and not Aperture (unless referenced)?
After hours of frustration and not having the latest version of iPhoto, I discovered that with my Aperture 3.5.1, I can right click on the image and use the "edit with" drop down, such as with Photoshop. Then from photoshop I can "command-click" on the top banner of the image and get the file path to where the original is located. I then created an alias of the folder where my original was and dragged it to my desktop for easy access.
This works because Aperture creates a second original located in the same Folder on our hard drives as the 1st original. To delete this second file that we used as a beacon to find our original, go to the same Project in Aperture and select this file that will have a badge on it and then in the File menu select "Delete Original Image and All Versions." The file will now be in our "Aperture Trash", which then needs to be emptied in order to send it to our Mac Trash. Empty our Mac's trash to finish the job.