Well, maybe I'm confused as to what you're wanting to do. If you want to use the 1/2 port for a low pressure hose, get the 1/2 male to 3/8 female adapter. If you just want to plug the port, get a 1/2 port plug.
Edit: OK I see that is much lower profile. Does it go from 1/2 to 3/8?
Edit: OK I see that is much lower profile. Does it go from 1/2 to 3/8?