Can't find any on line?
Barrels, shrouds, and barrel wrenches are still available from the Dan Wesson branch of CZ-USA. Gun shows are another good place to dig for barrels and shrouds, usually for a real good price as the number of customers looking for such an item is pretty limited.
The Model 44 / 744 was only made in one configuration so any DW 44 barrel and shroud set will work. You'll need a piece of shim stock to set the cylinder gap. .005 inch is a good place to start. If you don't shoot a lot of lead and clean the gun often, you can run the gap as low as .003 inches.
As Majic stated the 3 inch if ever made is a pretty rare duck, would believe it's a 4 inch barrel and shroud.
Take Care