WHERE IN THE HELL DO I GET ONE?
Oh, they're out there....for $300+ each. Probably Ferrari UK has them, if you can reach them. The new Ferrari Owners website lost all the links to the Ferrari Classic Parts catalogs, so until the links are re-established you'll have to contact Ferrari UK directly.
Ferrari UK didin't have them a year ago when I asked them. After months of looking I gave up and went with the F50 key that superceded the folding one. I put my original folding one away and use the new one day-to-day.
I don't use either of the original keys for my car, they stay safely tucked away in the drawer. I have the F50 key for the ignition and something I got from the locksmith for the doors.
One of the cool things with the folding keys is that when its folded over with the car running the prancing horse is in the correct upright position. My 328 came with 3 folding keys so I use one of them as my regular key.