The SIG P320 .45 ACP has been out for some time. But SIG does not list .45ACP as a caliber on their P320 Carry page, and I do not recall ever seeing one. As you probably know, the P320 Carry models all have compact length slides and barrels but a grip module with a full-length grip that excepts the full-sized magazines.
I have read that SIG came out with the Carry model in response to law enforcement agencies that wanted a pistol with a full-length grip and full-size magazine capacity, but a somewhat shorter slide and barrel for less weight and a quicker draw. It may be that not too many LEAs are interested in a .45 ACP duty pistol these days.
If a Carry sized P320 .45 ACP is really what you want, I would suggest buying a P320 compact .45 ACP. You could then get a full-sized P320 .45 grip module and some full size magazines. Cut the end off of the grip module to match your slide length. You could then switch your fire control unit from one grip module to the other. Obviously, the compact grip module would be a little easier to conceal. The full-size magazines would work fine in the compact grip module.