After many many years, and alas at quite a high price tag, I finally have found one of the hardest to find Takara PVCs.
Not only is it a chase figure, it is also considered a bonus figure as each piece was broken up with other full figures and you had to collect and track down all of them.
But finally. I have one! The first one I've ever seen.
Takara Scorponok PVC (chase/bonus figure) is the 1860th Transformer that I've acquired.