There is I believe one other Streethawk bike out there that ended up in private hands. Chris Bromham, one of the original show stunt riders (a UK based bike stuntman) restored one of the bikes used in the series. Here you can find him riding it in a video (wearing one of the Street Hawk costumes). I am pretty sure it is a different bike from what Cars of the Stars had as I saw that bike in person back in 2004. Both bikes look pretty similar though (Chris' bike seems blacker in color than the deep dark metallic look of the museum bike, indicating one might have been a hero bike and the other a stunt bike)
One that was stripped down sold a few months back. In the photo used to sell it the fiberglass nosecone was still attached. But after speaking with the seller it was discovered that it was a old photo and the bike had been fully stripped of its custom parts.
That was only the 2nd bike I've discovered since starting to search in 1997.