In my case the water pump inlet is not the same size as the radiator outlet so I have to use an adaptor anyway. When it comes to simple round parts I like to build my own if for no other reason than to justify owning a lathe.........It may take me 6 hours in the garage, but I'll be able to tell my wife that I saved $40.
No wonder I'm at 8 years into this build and not done yet.
-Jon