I just checked the website.
Currently, only Nitron and Two-tone are listed as possible finishes for the P226. When you click the link, it shows you ALL available finishes (since all stainless is now available on P220's and Sports, they put a pic up) for ALL sigs.
I promise you, this thing had some aftermarket work done on it. If you call Sigarms, they will give you a first ship date for the P226ST. Sometime in May or June, IIRC.