They did! I got lucky enough to find one of them a few years ago. The model was 220R-45-SBSS, and it was in the same 37B prefix as the 220 10mms, same front checkering, etc.
Funnily enough, cruising one of the Sig forums, apparently a known issue on higher round count steel frame 45s is parts breakages - since the steel frame has less "give" than the alloy frames, the forces get transferred more to the smaller parts, which break more often...
Pardon the dirt and schmutz on it, I just dug it out for some photos for a proof of life (and to make sure I didn't forget in which stack of crap in the safe it was buried in):
Edit - if you have money coming out of your ears, you could of course just buy the 10mm, replace the locking block with a 45, and swap a 45 upper onto it...it'd be an expensive way to get you there, but you'd get a steel framed 45 that way...