[trebleshot]

It may only be a retail release in Australia. Exclusives in one country aren't always offered in the same way in another country. For example, a chromed version of the TF ROTF Ravage mold ("Recon Ravage") was a mail-away exclusive in the US, but was available at regular retail in both Canada and Australia.

EDIT: And since that version of Shredder was an SDCC exclusive here, I sincerely doubt we will see it offered at US retail. The mold may get re-used for a future retail release, but it will not be the same as the SDCC version (like some of the MU exclusives from SDCC in previous years).