The R2X with ETM in the Prodigy is much stronger than the Accu-Tread particle in the xfactor Ace.
Also, the Ace is asymmetric, while the Prodigy is symmetric. Barring finding an NIB Ace for several hundred dollars or another of the xfactor balls, the closest thing that you might be able to find is an original Shift, which is R2S pearl particle (and I have 2 of them).