My guess is either they never shot it in the first place or the footage has been lost since the movie was made 35 years ago now.
There are quite a few changes from the "final" screenplay that came with the Blu-Ray and the finished product. My hunch is that the film's producer saw the scene in the script, said "if we do it that way, we'll get an R-rating, and we need this to be PG-13", and then insisted that they rewrite the scene to avoid full nudity. If he did this before they actually shot the scene, then there might have been no footage of full nudity shot at all. Filming a scene that you knew would never make it into the movie, particularly one like this that uses a fair amount of practical special effects that probably aren't cheap, might be too much of a waste of money for the producer to allow the director to go forward with it.
When the editor talks about his original version being "slightly perverted" before being cut down, I wonder what he means. It might simply mean that they had the actress failing around topless a little bit longer, or that they originally showed her shoes, stockings, and bra each coming off. (You only see her skirt and her blouse actually come off of her; all the rest of her clothing gets removed off camera.)
If I had to bet money, I would wager that full nudity for that scene was never shot in the first place, and therefore there is no footage to find.
I hope someone proves me wrong.

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