I think the last header I installed was for a CJ7. I bought a Pace Setter and it worked great. I know there are several brands out there. I would just search for headers, write down the brands and then search for reviews in a 2003 Rubicon and see what pops up. There may be others in the club, like Bob, that has more experience with them and can probably provide you with a direction.
Edit: Looks like Bob was typing the same time I was.