I imagine Colt Officers Model barrels would be a bit difficult to find I guess the internet is the place to start. Star PD barrels would probably be available from one of the large used parts dealers. Barrels just might need to be fitted.
There are plenty of .22LR conversion kits for the full size M1911. Not sure for other models.
I don’t think a .45 auto can be converted to 9mm. At one time it was possible to convert 9mm M1911s to .38 Super then back to 9mm if you wanted.
The conversion kit I was looking at some time ago had a modified lip with the new barrel for proper feed of the 9mil ammo, so that with the slide, spring, and of course mag change were all that was required.