How about that!
I contacted Starline almost 20 years ago to try and convince them to make 455 brass.
But, honestly,
I find the best stuff is that you make yourself. S&W 2nd model Hand Ejectors have fairly long chambers, even a bit long for the 455 Colt ammo that C.I.L. Dominion made in Canada. (Note: this was the best factory brass for 455 I've personally used, even with the balloon head.)
I find it best to determine chamber length, then cut down 45 Colt brass to perhaps .010-.020" under that length. Of course, you have to account for the amount needed to thin the rim in the process. Standard specs state the 455 uses a .040" rim, but I find .045" gives enough clearance and probably gives a bit of a benefit accuracy-wise by tightening up headspace.
Anyhow, it's a lot of extra work, but you can customize your brass to fit your cylinder.
Nonetheless, it'll be nice to see some good factory 455 brass. I hope they use a large primer pocket and don't repeat Fiocchi's mistake of using a small primer.
Thanks for the note!
Jim